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Machine Breakdown Recovery - Absolute-Beginner Level: core concept mastery Machine Breakdown Recovery ABSOLUTE BEGINNER

This skill primer 🌟 worksheet focuses on Machine Breakdown Recovery - a key topic in Scheduling. You'll solve 20 absolute-beginner-level problems (Worksheet 1 of 10). The primary focus is on core concept mastery. Master machine breakdown recovery problems, machine breakdown recovery reasoning questions, and machine breakdown recovery practice through systematic practice.

📝 Worksheet 1 of 10 • 20 questions • ⏱️ Estimated time: 20 minutes • 🎯 Absolute Beginner level

What you'll learn in this worksheet:
Your progress through Machine Breakdown Recovery
Worksheet 1 of 10 (0% complete)

Question 1

A machine needs to process 4 jobs. Processing times: - Job A: 70 minutes - Job C: 55 minutes - Job D: 70 minutes - Job E: 64 minutes The machine breaks down at 109 minutes and takes 28 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job C → Job E → Job A → Job D
2. Simulate processing with breakdown:
- Job C: 0 → 55
- Job E: Starts at 55, breakdown at 109 (54 min completed), repair 28 min, resume 10 min → completes at 147
- Job A: 147 → 217
- Job D: 217 → 287

3. Total makespan: 287 minutes
4. Delay caused by breakdown: 28 minutes

Answer: 287 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 2

A machine needs to process 4 jobs. Processing times: - Job D: 31 minutes - Job B: 62 minutes - Job A: 55 minutes - Job E: 61 minutes The machine breaks down at 115 minutes and takes 29 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job D → Job A → Job E → Job B
2. Simulate processing with breakdown:
- Job D: 0 → 31
- Job A: 31 → 86
- Job E: Starts at 86, breakdown at 115 (29 min completed), repair 29 min, resume 32 min → completes at 176
- Job B: 176 → 238

3. Total makespan: 238 minutes
4. Delay caused by breakdown: 29 minutes

Answer: 238 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 3

A machine needs to process 4 jobs. Processing times: - Job C: 69 minutes - Job E: 30 minutes - Job B: 81 minutes - Job D: 75 minutes The machine breaks down at 109 minutes and takes 19 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job E → Job C → Job D → Job B
2. Simulate processing with breakdown:
- Job E: 0 → 30
- Job C: 30 → 99
- Job D: Starts at 99, breakdown at 109 (10 min completed), repair 19 min, resume 65 min → completes at 193
- Job B: 193 → 274

3. Total makespan: 274 minutes
4. Delay caused by breakdown: 19 minutes

Answer: 274 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 4

A machine needs to process 4 jobs. Processing times: - Job C: 40 minutes - Job A: 54 minutes - Job D: 63 minutes - Job B: 53 minutes The machine breaks down at 97 minutes and takes 27 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job C → Job B → Job A → Job D
2. Simulate processing with breakdown:
- Job C: 0 → 40
- Job B: 40 → 93
- Job A: Starts at 93, breakdown at 97 (4 min completed), repair 27 min, resume 50 min → completes at 174
- Job D: 174 → 237

3. Total makespan: 237 minutes
4. Delay caused by breakdown: 27 minutes

Answer: 237 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 5

A machine needs to process 4 jobs. Processing times: - Job D: 67 minutes - Job A: 41 minutes - Job B: 31 minutes - Job E: 48 minutes The machine breaks down at 92 minutes and takes 42 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job B → Job A → Job E → Job D
2. Simulate processing with breakdown:
- Job B: 0 → 31
- Job A: 31 → 72
- Job E: Starts at 72, breakdown at 92 (20 min completed), repair 42 min, resume 28 min → completes at 162
- Job D: 162 → 229

3. Total makespan: 229 minutes
4. Delay caused by breakdown: 42 minutes

Answer: 229 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 6

A machine needs to process 4 jobs. Processing times: - Job C: 57 minutes - Job D: 86 minutes - Job E: 44 minutes - Job A: 57 minutes The machine breaks down at 98 minutes and takes 18 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job E → Job C → Job A → Job D
2. Simulate processing with breakdown:
- Job E: 0 → 44
- Job C: Starts at 44, breakdown at 98 (54 min completed), repair 18 min, resume 3 min → completes at 119
- Job A: 119 → 176
- Job D: 176 → 262

3. Total makespan: 262 minutes
4. Delay caused by breakdown: 18 minutes

Answer: 262 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 7

A machine needs to process 4 jobs. Processing times: - Job D: 44 minutes - Job A: 49 minutes - Job E: 53 minutes - Job C: 66 minutes The machine breaks down at 80 minutes and takes 25 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job D → Job A → Job E → Job C
2. Simulate processing with breakdown:
- Job D: 0 → 44
- Job A: Starts at 44, breakdown at 80 (36 min completed), repair 25 min, resume 13 min → completes at 118
- Job E: 118 → 171
- Job C: 171 → 237

3. Total makespan: 237 minutes
4. Delay caused by breakdown: 25 minutes

Answer: 237 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 8

A machine needs to process 4 jobs. Processing times: - Job E: 73 minutes - Job B: 60 minutes - Job C: 72 minutes - Job A: 36 minutes The machine breaks down at 91 minutes and takes 20 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job A → Job B → Job C → Job E
2. Simulate processing with breakdown:
- Job A: 0 → 36
- Job B: Starts at 36, breakdown at 91 (55 min completed), repair 20 min, resume 5 min → completes at 116
- Job C: 116 → 188
- Job E: 188 → 261

3. Total makespan: 261 minutes
4. Delay caused by breakdown: 20 minutes

Answer: 261 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 9

A machine needs to process 4 jobs. Processing times: - Job C: 66 minutes - Job E: 52 minutes - Job B: 42 minutes - Job A: 84 minutes The machine breaks down at 77 minutes and takes 29 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job B → Job E → Job C → Job A
2. Simulate processing with breakdown:
- Job B: 0 → 42
- Job E: Starts at 42, breakdown at 77 (35 min completed), repair 29 min, resume 17 min → completes at 123
- Job C: 123 → 189
- Job A: 189 → 273

3. Total makespan: 273 minutes
4. Delay caused by breakdown: 29 minutes

Answer: 273 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 10

A machine needs to process 4 jobs. Processing times: - Job A: 58 minutes - Job C: 50 minutes - Job E: 81 minutes - Job D: 48 minutes The machine breaks down at 96 minutes and takes 33 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job D → Job C → Job A → Job E
2. Simulate processing with breakdown:
- Job D: 0 → 48
- Job C: Starts at 48, breakdown at 96 (48 min completed), repair 33 min, resume 2 min → completes at 131
- Job A: 131 → 189
- Job E: 189 → 270

3. Total makespan: 270 minutes
4. Delay caused by breakdown: 33 minutes

Answer: 270 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 11

A machine needs to process 4 jobs. Processing times: - Job D: 34 minutes - Job B: 73 minutes - Job C: 44 minutes - Job E: 47 minutes The machine breaks down at 79 minutes and takes 18 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job D → Job C → Job E → Job B
2. Simulate processing with breakdown:
- Job D: 0 → 34
- Job C: 34 → 78
- Job E: Starts at 78, breakdown at 79 (1 min completed), repair 18 min, resume 46 min → completes at 143
- Job B: 143 → 216

3. Total makespan: 216 minutes
4. Delay caused by breakdown: 18 minutes

Answer: 216 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 12

A machine needs to process 4 jobs. Processing times: - Job E: 80 minutes - Job D: 53 minutes - Job A: 49 minutes - Job B: 65 minutes The machine breaks down at 84 minutes and takes 42 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job A → Job D → Job B → Job E
2. Simulate processing with breakdown:
- Job A: 0 → 49
- Job D: Starts at 49, breakdown at 84 (35 min completed), repair 42 min, resume 18 min → completes at 144
- Job B: 144 → 209
- Job E: 209 → 289

3. Total makespan: 289 minutes
4. Delay caused by breakdown: 42 minutes

Answer: 289 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 13

A machine needs to process 4 jobs. Processing times: - Job C: 64 minutes - Job D: 36 minutes - Job B: 54 minutes - Job A: 41 minutes The machine breaks down at 77 minutes and takes 16 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job D → Job A → Job B → Job C
2. Simulate processing with breakdown:
- Job D: 0 → 36
- Job A: 36 → 77
- Job B: Starts at 77, breakdown at 77 (0 min completed), repair 16 min, resume 54 min → completes at 147
- Job C: 147 → 211

3. Total makespan: 211 minutes
4. Delay caused by breakdown: 16 minutes

Answer: 211 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 14

A machine needs to process 4 jobs. Processing times: - Job A: 37 minutes - Job E: 38 minutes - Job C: 77 minutes - Job D: 44 minutes The machine breaks down at 115 minutes and takes 27 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job A → Job E → Job D → Job C
2. Simulate processing with breakdown:
- Job A: 0 → 37
- Job E: 37 → 75
- Job D: Starts at 75, breakdown at 115 (40 min completed), repair 27 min, resume 4 min → completes at 146
- Job C: 146 → 223

3. Total makespan: 223 minutes
4. Delay caused by breakdown: 27 minutes

Answer: 223 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 15

A machine needs to process 4 jobs. Processing times: - Job B: 71 minutes - Job A: 53 minutes - Job C: 46 minutes - Job E: 59 minutes The machine breaks down at 116 minutes and takes 44 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job C → Job A → Job E → Job B
2. Simulate processing with breakdown:
- Job C: 0 → 46
- Job A: 46 → 99
- Job E: Starts at 99, breakdown at 116 (17 min completed), repair 44 min, resume 42 min → completes at 202
- Job B: 202 → 273

3. Total makespan: 273 minutes
4. Delay caused by breakdown: 44 minutes

Answer: 273 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 16

A machine needs to process 4 jobs. Processing times: - Job B: 77 minutes - Job E: 79 minutes - Job D: 68 minutes - Job A: 70 minutes The machine breaks down at 83 minutes and takes 32 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job D → Job A → Job B → Job E
2. Simulate processing with breakdown:
- Job D: 0 → 68
- Job A: Starts at 68, breakdown at 83 (15 min completed), repair 32 min, resume 55 min → completes at 170
- Job B: 170 → 247
- Job E: 247 → 326

3. Total makespan: 326 minutes
4. Delay caused by breakdown: 32 minutes

Answer: 326 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 17

A machine needs to process 4 jobs. Processing times: - Job A: 64 minutes - Job E: 54 minutes - Job C: 55 minutes - Job D: 59 minutes The machine breaks down at 68 minutes and takes 30 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job E → Job C → Job D → Job A
2. Simulate processing with breakdown:
- Job E: 0 → 54
- Job C: Starts at 54, breakdown at 68 (14 min completed), repair 30 min, resume 41 min → completes at 139
- Job D: 139 → 198
- Job A: 198 → 262

3. Total makespan: 262 minutes
4. Delay caused by breakdown: 30 minutes

Answer: 262 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 18

A machine needs to process 4 jobs. Processing times: - Job C: 81 minutes - Job D: 30 minutes - Job B: 79 minutes - Job E: 55 minutes The machine breaks down at 74 minutes and takes 24 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job D → Job E → Job B → Job C
2. Simulate processing with breakdown:
- Job D: 0 → 30
- Job E: Starts at 30, breakdown at 74 (44 min completed), repair 24 min, resume 11 min → completes at 109
- Job B: 109 → 188
- Job C: 188 → 269

3. Total makespan: 269 minutes
4. Delay caused by breakdown: 24 minutes

Answer: 269 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 19

A machine needs to process 4 jobs. Processing times: - Job C: 76 minutes - Job A: 37 minutes - Job B: 30 minutes - Job E: 41 minutes The machine breaks down at 77 minutes and takes 37 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job B → Job A → Job E → Job C
2. Simulate processing with breakdown:
- Job B: 0 → 30
- Job A: 30 → 67
- Job E: Starts at 67, breakdown at 77 (10 min completed), repair 37 min, resume 31 min → completes at 145
- Job C: 145 → 221

3. Total makespan: 221 minutes
4. Delay caused by breakdown: 37 minutes

Answer: 221 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.

Question 20

A machine needs to process 4 jobs. Processing times: - Job B: 82 minutes - Job C: 70 minutes - Job A: 40 minutes - Job D: 65 minutes The machine breaks down at 89 minutes and takes 20 minutes to repair. Jobs are scheduled using Shortest Processing Time (SPT) first rule. What is the total completion time (makespan) after handling the breakdown?
Step-by-step solution (Breakdown Recovery):

1. Original SPT order: Job A → Job D → Job C → Job B
2. Simulate processing with breakdown:
- Job A: 0 → 40
- Job D: Starts at 40, breakdown at 89 (49 min completed), repair 20 min, resume 16 min → completes at 125
- Job C: 125 → 195
- Job B: 195 → 277

3. Total makespan: 277 minutes
4. Delay caused by breakdown: 20 minutes

Answer: 277 minutes

Key Strategy: Simulate the timeline, account for breakdown during active job processing.
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