3 The most common junior girl's clothing size is reported to be a Medium. Stores use a table like the one below to decide how many size Mediums to buy when it places an order on a new clothing item.

Total number items ordered Size Medium to order
40 10
60 15
80 20
Part A

What is the ratio of the number of size Medium items the store should order to the total number of items being ordered?
List the ratio in simplest form, without labels. Enter your answer with a colon (e. g. 1:1)

Part B
What percent of each order will be size Medium items?

%