Jamal traveled a distance of 520 miles in 9 hours. Part of the time, his rate of speed was 55 mph. The rest of the time his rate of speed was 60 mph. How long did Jamal travel at each rate?

jamal traveled 5 hours at 55mph and 4 hours at 60mph

Step-by-step explanation:

time x will be time jamal travels 55 mph (in hours)

time y will be time jamal travels 60 mph (in hours)

distanced traveled 520 miles

distance = time*speed

520= x*55+y*60

520=55x+60y

jamal traveled for 9 hours

9 hours is composed to the two times x and y

9=x+y

then

x=9-y

substitute into 520=55x+60y

520=55(9-y)+60y

520=495-55y+60y

520=495+5y

25=5y

y=5

x+y=9

x+5=9

x=4

time x is time jamal travels 55 mph (in hours)

time y is time jamal travels 60 mph (in hours)

jamal traveled 5 hours at 55mph and 4 hours at 60mph

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4