John needs $20 to buy a ticket to a show. He earned 1/4 of the money on Monday, 2/5 on Tuesday and 1/ 10 on

Question

Wednesday. What fraction of the money does John still need to earn?

Answer 1

you have to find the smallest mutual denominator then calculate what portion of the money is earned already.1/4, 2/5,1/10 4x5=20 - that is also divisible by 10 so no need to multiply by 10 also.. so he earned 1/4 =5/20 on monday, 2/5 = 8/20 on tuesday and 1/10 = 2/20 on wed. that is 5+8+2 =15/20
so he needs 5/20 more (what is $5 out of $20)