Section: Mathematical Reasoning

67) Alter working 4 hours, Frank has made 21 machine parts. At the same rate, how many parts can he make in 7 hours?

1. 7(21) / 4
2. 7(4) /21
3. 7(21)
4. 4(21) / 7
5. 7(4)(21)

Let x = number of machine parts Frank can make in 7 hr.

Set up a proportion:
4 / 21 = 7 / x
4x = 7(21)
x = 7(21) /4