Question

A man's age after 15 years will be the square of his age 15 years ago. What is it's present year ​

Answer 1

ANSWER--

Let the man’s present age = x.

x+15 = (x-15)^2, or

x+15 = x^2–30x+225, or

x^2–31x+210 = 0

(x-21)(x-10) = 0

x = 21 or 10. Here 10 has no relevance.

So the man is 21 years now,

Check: (21–15) = 6^2 = 36 same as 21+15 or 36. Correct.

It was very easy I hope it helps

Answer 2

Solution:

Let x be his present age.

Man’s age after 15 years = x + 15

Man’s age 15 years ago = x - 15

x + 15 = (x - 15)^2

x + 15 = x^2 - 30x + 225

x^2 - 30x - x + 225 - 15 = 0

x^2 - 31x + 210 = 0

(x - 21) (x - 10) = 0

x = 21 or 10

We get x = 21 and x = 10

The correct answer is x = 21 because we use x = 10 it will be rejected because 15 years ago he wasn't even born if his age is 10.

Hope this would help.