Mr Luis bought some pizzas for a group of pupils. There was an equal number of girls and boys. The girls received 2 times as many pizzas as the boys. Each boy ate ¹₅ of a pizza and the boys finished all the pizzas given to them. Each girl ate ¹₁₅ of a pizza and the girls had 13¹₃ pizzas left. How many pizzas did Mr Luis buy?

	Girls (1)	Boys (2)
Before	2 u	1 u
Change	- 1 p	- 3 p
After	200	0

¹₅ = ³₁₅

Cutting the slices of pizzas into same size. Each pizza was cut into 15 slices. Every girl ate 1 slice of pizza and every boy ate 3 slices of pizza.

Number of slices that the girls had left
= 13¹₃ ÷ ¹₁₅ 
= ⁴⁰₃ x 15
= 200

2 u - 1 p = 200 --- (1)

1 u - 3 p = 0
1 u = 3 p --- (2)

Make u the same.

(2)_x2
2 u = 6 p --- (3)

Substitute (3) into (1).
2 u - 1 p = 200
6 p - 1 p = 200
5 p = 200

1 p = 200 ÷ 5 = 40

Total number of slices of pizzas for girls
= 200 + 1 p
= 200 + 40
= 240

Total number of slices of pizzas for boys
= 240 ÷ 2
= 120

Total number of slices of pizzas for pupils
= 240 + 120
= 360

Total number of pizzas that Mr Luis bought
= 360 ÷ 15
= 24

Answer(s): 24