Question

A grocer took a random survey of 40 customers. Twelve customers would like the store to stay open later. Suppose the grocer surveyed 100 more customers. How many of those customers would likely want the store to stay open later?

Answer 1

$\frac{12}{40} = \frac{x}{100}$ is the equation to solve for the proportion of 12 out of 40 is what to x out of 100.

So you cross multiply and get
1200=40x
Divide by 40
x=30

So 30 out of 100 people would want the store to stay open later.

Answer 2

60 out of 100 customers would likely want the store to stay open later. Since, 12/40 customers would want it open later it's the same as 6/20 customers wanting it open later (divide 12 and 40 by 2). Now you'd take 20*5= 100 and 6*5= 30... 100 is your denominator and 30 is your numerator