SOLUTION: A man walks for 12 km at x km/h and then jogs for another 12 km at (x + 2) km/h. He travels for a total of 5 hours. Find the value of x.

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Question 604533: A man walks for 12 km at x km/h and then jogs for another 12 km at (x + 2) km/h. He travels for a total of 5 hours. Find the value of x.
Answer by alicealc(293) About Me  (Show Source):
You can put this solution on YOUR website!
speed = distance/time
so, time = distance/speed

12%2Fx+%2B+12%2F%28x%2B2%29=5
%2812%2A%28x%2B2%29%2B12%2Ax%29%2F%28x%2A%28x%2B2%29%29=5
%2812x%2B24%2B12x%29%2F%28x%5E2%2B2x%29=5
24x%2B24=5%2A%28x%5E2%2B2x%29
24x%2B24=5x%5E2%2B10x
0=5x%5E2%2B10x-24x-24
0=5x%5E2-14x-24
0 = (5x + 6)*(x - 4)
5x + 6 = 0 or x - 4 = 0
5x = -6 or x = 4
5x = -6/5 or x = 4
because the speed can't be a negative number, we choose x = 4

so, x = 4