Question

Carol ate 2/5 of the cake. Dima ate 3/5 of the REMAINING CAKE, mom ate the rest.

Answer 1

"How many times more did Carol eat compared to Dima?" is quite different from the previous question, in which you asked "how much more did Carol eat than Dima?"  I think they ate 10/25 and 9 /25 of the cake, respectively.

10/25 is greater than 9/25, obviously.  We need to calculate "how many times greater is 10/25 than 9/25?  So we divide 9/25 INTO 10/25.  This comes out to 10/9, or 1.11 times as much.  Carol eats 11% more cake than Dima.  Hope she doesn't gain too much extra weight.   ;)