A certain car can travel 72 kilometers on a liter of fuel. If the fuel tank’s contents decrease by 3.9 gallons over a period of 5.7 hours as the car moves at a constant speed, how fast is the car moving, in miles per hour? (1 gallon = 3.8 liters; 1 mile = 1.6 kilometers)  Choose the correct choice:
A) 52
B) 65
C) 117
D) 91
E) 104
Fuel used 3.9 gallons ;convert to liters--&gt; 3.9 x 3.8 liters   Time = 5.7 hours   1 mile = 1.6 kilometers ;convert to miles--&gt; 1km = 1/1.6 mile   Speed (km/hour)  --  1= 
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1/1.6 mile   Speed (km/hour)= D/T = 72 (km*) x 3.9 x 3.8 / 5.7   replace (km*) to miles ; multiply by 1/1.6 mile   Speed (miles/hour)= 72x 3.9 x 3.8 / 5.7 x 1.6 = 78 miles/hour   Ans :117   PS :i felt the factors were easy to cancel out ,so didn't require much rounding off   = 72 x 3.9 x 3.8 / 5.7 x 1.6   = 117 117
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A certain car can travel 72 kilometers on a liter of fuel. If the fuel tank’s contents decrease by 3.9 gallons over a period of 5.7 hours as the car moves at a constant speed, how fast is the car moving, in miles per hour? (1 gallon = 3.8 liters; 1 mile = 1.6 kilometers)