Math problem Kaplan glitch

[laundry]

Advertisement - Members don't see this ad

A new eight-lane highway costs $7,500,000 per mile
(5280 feet). If each lane measures 11 feet across, how
much would it cost to pave a square mile of highway?
A. $85,227
B. $450,000,000
C. $600,000,000
D. $3,600,000,000
E. $4,950,000,000

B:
Each lane is 11 feet across and there are 8 lanes, so its width is 88 feet. 5280 ÷ 88 = 60 , so 60 miles
of this highway would represent one square mile of highway. 60 × $7,500,000 = $450,000,000, so it
would cost $450,000,000 to pave one square mile of highway.

It's 60 feet, not miles!!!! isn't it? ​

 

[Streetwolf]

60 miles, you have your units all messed up.

You did 5280 ft / 88 ft = 60 ft but that doesn't make sense because the units should be canceling each other out according to that equation.

You need 1 sq mile = (5280 ft)^2 = (5280*5280) ft^2.

Then you have (5280*5280) ft^2 / 88 ft = (5280*60) ft. (Since 5280/88 = 60.)

Convert this into miles: (5280*60) ft * (1 mi / 5280 ft) = 60 mi.