SOLUTION: Please help me with this problem. "While training for a biathlon race, Kevin covered a total distance fo 9km by swimming for 45 minutes and running for 20 minutes. The next day he
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Question 548934: Please help me with this problem. "While training for a biathlon race, Kevin covered a total distance fo 9km by swimming for 45 minutes and running for 20 minutes. The next day he swam for 30 minutes and ran for 40 minutes. Find his rates (in km/h) for swimming and running (assume these rate are contant). Thanks! Answer by mananth(16946) (Show Source):
You can put this solution on YOUR website! swimming rate = s
running rate =r
d=r*t
convert minutes to hours
First day
(3/4)s+(1/3)r = 9
LCD = 12
multiply equation by 12
9s+4r=108...............(1)
Day II
(1/2)s+(2/3)r= 9
LCD = 6
multiply equation by 6
3s+4r=54....................(2)
9 s + 4 r = 108 .............1
3 s + 4 r = 54 .............2
Eliminate r
multiply (1)by -1
Multiply (2) by 1
-9 s -4 r = -108
3 s + 4 r = 54
Add the two equations
-6 s = -54.00
/ -6
s = 9
plug value of s in (1)
9 s + 4 r = 108
81 + 4 r = 108
4 r = 108 -81
4 r = 27
r = 6 3/ 4
swimming rate 9 km/h
running rate 6 3/4 km/h
