Question

Keith is choosing between two exercise routines. In Routine #1, he does only running, burning 8.5 calories per minute. In Routine #2, he burns 19 calories walking. He then runs at a rate that burns 3.75 calories per minute. For what amounts of time spent running will Routine #1 burn more calories than Routine #2? Use for the number of minutes spent running, and solve your inequality for .

Answer 1

Answer x > 4

Routine 1: 8.5x

Routine 2: 19 + 3.75x

We want to know when the total for routine 1 > the total for routine 2, so now we put those expressions into an inequality.

8.5x > 19 + 3.75x
4.75x > 19
x > 19/4.75
x > 4

Checking the math
8(4) > 19 + 3.75(4)
32 > 19 + 15
32 > 34 This confirms 4 minutes isn’t enough.

8(5) > 19 + 3.75(5)
40 > 19 + 18.75
40 > 37.75