Question

Write a system of equations to describe the situation below, solve using any method, and fill in the blanks.

When Ellen does 19 push-ups and 8 sit-ups, it takes a total of 43 seconds. In comparison, she needs 48 seconds to do 12 push-ups and 12 sit-ups. How long does it take Ellen to do each kind of exercise?

It takes Ellen _ seconds to do a push-up and _seconds to do a sit-up.

Thank you :

Answer 1

push-up = 1 second

sit-up = 3 seconds

Explanation:

let p represent the # of push-ups

let s represent the # of sit-ups

System of equations:

19p+8s=43

12p+12s=48

i'll eliminate s by multiplying the top equation by 3 and the bottom equation by -2

57p+24s=129

-24p-24s=-96

33p=33

p=1 second

now solve for s (i'll plug p into the 2nd equation)

12(1) + 12s=48

12s=36

s=3 seconds