Mary 's car will go 261 miles on 14.5 gallons of gasoline in highway driving.

a) How many gallons will it take to drive 1641 miles from her house to a friend's house?

b) How far can the car be driven on 139 gallons of gasoline?

a) 91 1/6 gallons

b) 2502 miles

Step-by-step explanation:

You are given a number of miles and a number of gallons for the car. The ratio of these numbers is ...

(261 mi) / (14.5 gal) = 18 mi/gal

We presume this value is constant for this car. Then the questions can be answered by forming and solving a proportion:

a) 1641 miles / (gallons) = 18 mi / (1 gal)

Multiplying by gallons and dividing by 18 mi/gal, we get

1641/18 gal = (gallons) = 91 1/6 gal

It will take 91 1/6 gallons of gasoline for Mary to drive to her friend's house.

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b) Same deal, but the miles are unknown.

(miles) / (139 gal) = (18 mi) / (1 gal)

Multiplying by 139 gal gives ...

(18 mi) ·139 = (miles) = 2502 mi

139 gallons of gasoline will let Mary drive 2502 miles.