SOLUTION: Burning Calories During strenuous exercise an athlete can burn 9 calories per minute on a stationary bicycle and 11.5 calories per minute on a stair climber. In a 30-minute workout

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Question 420402: Burning Calories During strenuous exercise an athlete can burn 9 calories per minute on a stationary bicycle and 11.5 calories per minute on a stair climber. In a 30-minute workout an athlete burns 300 calories. How many minutes does the athlete spend on each type of exercise equipment?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let a = minutes spent on bicycle
Let b = minutes spent on chair climber
---------
given:
(1) a+%2B+b+=+30
(2) +9a+%2B+11.5b+=+300+
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(2) 90a+%2B+115b+=+3000
(2) +18a+%2B+23b+=+600+
Multiply both sides of (1) by
18 and subtract (1) from (2)
(2) +18a+%2B+23b+=+600+
(1) -18a+-+18b+=+540+
5b+=+60
b+=+12
and, since
(1) a+%2B+b+=+30
a+=+30+-+12
a+=+18
18 minutes on bicycle and 12 minutes on stair climber
check answer:
(2) +9a+%2B+11.5b+=+300+
(2) +9%2A18+%2B+11.5%2A12+=+300+
+162+%2B+138+=+300
+300+=+300+
OK