Ratio Change Two Points

Ratio Change Two Points problems give the ratio of ages at two different points in time (e.g., present and future, or past and present). These require solving for present ages using both ratio conditions.

10Worksheets
200+Practice Questions
AdvancedDifficulty
3-4 hoursHours to Master

Introduction to Ratio Change Two Points

Ratio Change Two Points problems give the ratio of ages at two different points in time (e.g., present and future, or past and present). These require solving for present ages using both ratio conditions.

Prerequisites

Ratio concepts Two-point ratio equations Linear equations
Why This Matters: Ratio Change Two Points problems appear in advanced sections of competitive exams. They test multi-temporal reasoning.

How to Solve Ratio Change Two Points Problems

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Step 1: Let present ages be expressed with a variable (e.g., A=ak, B=bk)

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Step 2: Express ages at the other time point (add/subtract years)

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Step 3: Set up the second ratio equation

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Step 4: Cross-multiply and solve for k

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Step 5: Calculate both ages at both time points

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Step 6: Verify both ratio conditions

Pro Strategy: Use the same k for present ratio. The second ratio gives an equation to solve for k. The time gap between the two ratio points is key.

Example Problem

Example: The ratio of A's age to B's age is 3:4 now. After 10 years, the ratio becomes 4:5. Find present ages. Solution: Step 1: A = 3k, B = 4k Step 2: After 10 years: (3k+10)/(4k+10) = 4/5 Step 3: 5(3k+10) = 4(4k+10) → 15k+50 = 16k+40 → 50-40 = 16k-15k → 10 = k Step 4: A = 30, B = 40 years Answer: A=30, B=40 years

Pro Tips & Tricks

  • If ratios are a:b (present) and c:d (after n years), then k = n(c-d)/(ad-bc)
  • If ratios are given for past and present, use subtraction
  • The ratio always moves toward 1:1 over time
  • Check if k is positive and yields reasonable ages
  • The older person's ratio term is usually larger initially
  • For two points, one equation is sufficient to find k

Shortcut Methods to Solve Faster

Formula: k = n(d-c)/(bc-ad) for a:b to c:d after n years
The difference between ratio terms decreases over time
Time gap × (difference in cross products) = k × (difference in ratio products)

Common Mistakes to Avoid

Using wrong ratio order (numerator/denominator swapped)
Forgetting to add/subtract years correctly
Cross multiplication errors
Not checking if the ratio increases or decreases appropriately

Exam Importance

Ratio Change Two Points is an important topic for various competitive exams. Here's how frequently it appears:

SSC CGL
1-2 questions
BANKING PO
1-2 questions
RAILWAYS RRB
1-2 questions

Ready to Master Ratio Change Two Points?

Start with Worksheet 1 and work your way up to expert level! Each worksheet includes:

20 practice questions
Detailed solutions
Step-by-step explanations
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