[Guest]

Back in the days, person A was 4 times as old as B.

Nowadays, person A is 40 years old. How old is B at this moment?

(Not hard, I know )

[Guest]

I'd like to try giving a shot .

B is 10 or 11 years old , because back in days, the age of A had to be divisible by 4. It could not be 39 , so it had to be 40 . At that time , B was 10 years old. And now , the age of B may be 10 or 11.

[bonanova]

Back = x years ago

[a-x] = 4[b-x] --> a = 4b-3x = 40

4[b-10] = 3x

[b-10] is a multiple of 3 = 3m; m is an integer

x is a multiple of 4 = 4n; n is an integer

12m = 12n; m = n

b = 3n+10

x = 4n

try n=1 => x=4 b=13 a=40

four years ago 36 = 4x9.

Check

B=13

[Guest]

There are 10 possible answers, assuming from the wording that it is possible for "back in the days" to be less than a year. The first possible age of B is 10. The next is 13, the next is 16, then 19, and so on up to 37.

[Guest]

There are 10 possible answers, assuming from the wording that it is possible for "back in the days" to be less than a year. The first possible age of B is 10. The next is 13, the next is 16, then 19, and so on up to 37.

Nice!! You found the solution, but, as ntdo was saying, there are more possible answers depending on when their birthday is.

[Guest]

Nice!! You found the solution, but, as ntdo was saying, there are more possible answers depending on when their birthday is.

10