How to solve this word problem: When Dad was 35 I was 7. Dad is now 3 times my age. How old are we?

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justaguide's profile pic

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

Let the age of the child be C and that of the father be F.

"When Dad was 35 I was 7"

=> D - C = 35 - 7 = 28

"Dad is now 3 times my age"

=> D = 3C

Substitute D = 3C in D - C = 28

=> 3C - C = 28

=> 2C = 28

=> C = 14

D = 3*14 = 42

The age of the child now is 14 and the age of the father is 42.

tonys538's profile pic

tonys538 | Student, Undergraduate | (Level 1) Valedictorian

Posted on

The problem gives that when the father was 35, the child was 7 and now the father's age is 3 times the child's age.

When the child was 7, the father was 35, this puts their age difference at 35 - 7 = 28. This does not change as the child gets older.

If the present age of the child is C and that of the father is F.

F = 3*C

F = C + 28

3*C = C + 28

2C = 28

C = 14

The present age of the child is 14 and the father is 42 years old.

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