Question

Joakim is icing 30 cupcakes. He spreads mint icing on 1/5 of the cupcakes and chocolate on 1/2 of the remaining cupcakes. The rest get vanilla icing. How many get vanilla icing?

Answer 1

The answer is 3/10

Explanation:

Let the fraction of cake that gets vanilla icing be 'm'

since the three fractions add up to a whole cake (1):

1/5 + 1/2 + m = 1

`(1)/(5) +(1)/(2) +m = 1`

`(1)/(7) + m=1`

∴
`m=1-(7)/(10) \\m=(3)/(10)`