John can jog twice as fast as he can walk. He was able to jog the first 5 miles to his grandmother's house, but then he tired and walked the remaining 2 miles. If the total trip took 0.9 hours, then what was his average jogging speed?

Solution

J o hn c an j o g tw i ce a s f a s t a s h e c an w a l k . He w a s ab l e t o j o g t h e f i rs t 5 mi l es t o hi s g r an d m o t h e r^{'} s h o u se, b u t t h e n h e t i re d an d w a l k e d t h e re mainin g 2 mi l es . I f t h e t o t a l t r i p t oo k 0.9 h o u rs, t h e n w ha t w a s hi s a v er a g e j o gg in g s p ee d ?

joging speed : 10

Solution steps

Translate the problem into an equation:

\frac{5}{x} + \frac{2 ^{2}}{x} = 0.9

Solve for

x, \frac{5}{x} + \frac{2 ^{2}}{x} = 0.9 : x = 10

joging speed : 10