math
posted by Alex .
Which equivalent fraction would you have to use in order to add 3/5 to 21/25

convert to common denominator
least commmon multiple of 5 and 25 is 25
so we want the fraction 3/5 to convert into the form x/25
so, 3/5 = x/25
we can cross multiply to get 5x = 25*3
x = 5*3
x= 15
So the fraction would be 15/25
Optional: adding 15/25 to 21/25 = 36/25 or 1 11/25 
3/5 to 21/25