Asked by Please help

10. Mary's travel time and speed vary INVERSELY. Mary drives home from work in 40 minutes driving 55 mph. If Mary needs to get home in 35 minutes, how fast does she need to drive? (Rounded to the nearest whole number!)
Answered by Anonymous
time = constant / speed
t = k/s
40 = k / 55
k = 2200
so
t = 2200 / s
35 = 2200 / s
s = 2200/35 = 62.86 or 63 mph
Answered by DrBob222
distance = rate x time
d = 55 mph x (40/60) = 36.6 miles to her house.
Then 36.6 = rate x (35/60) so rate = 36.6 x 60/35 = ? mph
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