Question

Pieter wrote and solved an equation that models the number of hours it takes to dig a well to a level of 72 feet below sea level.

7h – 5(3h – 8) = –72
Which statement is true about Pieter’s solution?

It cannot be a fraction or decimal because the depth of the well is a whole number.
It must be a positive number since it represents a number of hours.
It must be a negative number because the depth is below sea level.
It cannot be greater than –72 because that is the depth of the well.

Answer 1

Solve: 7h − 5(3h − 8) = −72
7h − 15h + 40 = −72
−8h + 40 = −72
−8h = −112
h = 14

h = 14, which is positive. So the true statement is: "It must be a positive number since it represents a number of hours."