JOe goes to the gym to run and swim. When running he burns 35 calories per minut, and when he swims he burns 30 calories per minute. He has burned 730 calories after exercising for a total of 23 min. How long on each activity?
Let Joe runs for x minutes,
and he swims for (23-x) minutes.
Number of calories burnt in running is 35*x,
And the number of calories burnt in swimming is 30*(23-x).
Joe burns 730 calories in total (running plus swimming).
35x + 30(23-x) = 730
`rArr` 35x + 690 - 30x = 730
`rArr` 5x = (730-690) = 40
`rArr` x = 40/5 = 8.
So, Joe runs for 8 minutes and swims for (23-8) = 15 minutes.