Question

if 1/5 of cakes where fruit and reminder was sponge what's the reminder in %

Answer 1

If 1/5 of the cakes are fruitcakes, then $1- \frac{1}{5} = \frac{4}{5}$ of the cakes are sponge cakes.  To convert to a percentage, we simply multiply by 100, for a result of $\frac{4}{5}*100= \frac{400}{5}=80$ percent sponge cakes.