Problem Solving

The number of stamps that kaye and alberto had were 5:3, after kaye gave alberto 10 of her stamps, the ratio were 7:5. Kaye had how many stamps more than alberto?

a)10
b)20
c)40
d)50
e)60




The right answer is c, but i don't know why i got e

this is my solution:

Kaye stamps=x alberto stamps =y

first equation x/y=5/3

second equation (x-10)/(y+10)=7/5


5y=3x----->3x-5y=0 from first equation


7y+70=5x-50---->5x-7y=120 from second eqaution



solving it i got x= 150 and y=90, thus the difference is 60 but why the answer is 40.......thanks

I don't see anything wrong in your approach.

X is 150 and Y is 90, and you have deduced X - Y
But the question (probably) asks for (X-10) - (Y+10) i.e, after 10 stamps are given.

So after 10 stamps are given kaye has 140, alberto has 100, diff is 40.

Folk, we have to give the present difference between their stamps

Presently K has 140 and has 100. So the difference is 40

bravotalks wrote:I don't see anything wrong in your approach.

X is 150 and Y is 90, and you have deduced X - Y
But the question (probably) asks for (X-10) - (Y+10) i.e, after 10 stamps are given.

So after 10 stamps are given kaye has 140, alberto has 100, diff is 40.

thanks, that make it clear