Multiple choice

Present age of Bob is equal to Abby’s age 8 years ago. Four year hence, the respective ratio between Bob’s age and Abby’s age will be 4: 5 at that time. What is Bob’s present age?

  1. 24 years

  2. 32 years

  3. 40 years

  4. 20 years

  5. 28 years
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Let Bob's present age be B and Abby's present age be A. From 'Bob's present age equals Abby's age 8 years ago': B = A - 8. In 4 years, the ratio is 4:5, so (B+4)/(A+4) = 4/5. Substituting B = A - 8 gives (A-4)/(A+4) = 4/5. Cross-multiplying: 5(A-4) = 4(A+4), which simplifies to 5A - 20 = 4A + 16, giving A = 36. Therefore B = 36 - 8 = 28 years.

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