Question

Twelve people can build 30 chairs in 8 hours. How many chairs can the people build in 100 hours? A) 3.75 B) 100 C) 150 D) 375

Answer 1

$\frac{30}{8}$ = $\frac{X}{100}$
Simply cross multiply.
3000 = 8x
Divide by 8
X = 375, so D.

Answer 2

There are several ways you can complete this problem.   They can complete 30 chairs in 8 hours.  You want to know how many chairs they can build in 100 hours.  So you can divide 100/8=12.5.  so you can multiply 12.5 x 30 chairs=375 chairs can be built.

so your answer is 375 (D)