You plan a party. You want to invite 30 children. You want to give them each one fifth of pizza.

Question

How many pizzas do you need?
You have one pizza left after the party. How many children did not come?

Answer 1

To give each of the 30 children one fifth of pizza, you need a total of:

30 x 1/5 = 6 pizzas

If you have one pizza left after the party, it means you only used:

6 - 1 = 5 pizzas

To find out how many children did not come, you need to know how many fifths of pizza are in one pizza:

1 pizza = 5/5

So if you had 5 pizzas, that means you had:

5 x 5/5 = 25 fifths of pizza

Since you wanted to give each child one fifth of pizza and you have 25 fifths of pizza, it means:

25 children came to the party

Therefore, the number of children that did not come is:

30 - 25 = 5 children.