Question

Maria is planning a party. Nancy, her friend, suggests that she
should order 3 pizzas for every 7 people. If she is expecting 21
people at the party, how many pizzas should she order?

Answer 1

Answer:

9 pizzas

Step-by-step explanation:

Maria is planning a party. She should order 3 pizzas for every 7 people. Let x be the number of pizzas Maria will order for 21 people, then

3 pizzas - 7 people

x pizzas - 21 people

Write a proportion:

$\dfrac{3}{x}=\dfrac{7}{21}$

Cross multiply:

$7\cdot x=21\cdot 3\\ \\7x=63\\ \\x=\dfrac{63}{7}=9\ pizzas$