Multiple choice

The age of a man is 3 times of his son. 15 year ago, the man was 9 times as old as his son. What will the age of the man after 15 year?

  1. 45 year

  2. 60 year

  3. 75 year

  4. 65 year
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

"the man is 3 times as old as his son" ___ f = 3s "15 years ago, the man was 9 times as old as his son was then" ___ f - 15 = 9(s - 15) substituting ___ 3s - 15 = 9(s - 15) distributing ___ 3s - 15 = 9s - 135 adding 135 - 3s ___ 120 = 6s dividing by 6 ___ 20 = s substituting ___ f = 3(20) = 60 Therefore, after 15 years, the age of the man will be = 60 + 15 = 75 years.

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