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During a trip that they took together, Carmen, Juan, Maria,

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During a trip that they took together, Carmen, Juan, Maria,

by BTGmoderatorDC » Fri Apr 05, 2019 6:35 pm

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During a trip that they took together, Carmen, Juan, Maria, and Rafael drove an average (arithmetic mean) of 80 miles each. Carmen drove 72 miles, Juan drove 78 miles, and Maria drove 83 miles. How many miles did Rafael drive?

A. 80

B. 82

C. 85

D. 87

E. 89

OA D

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by Brent@GMATPrepNow » Sat Apr 06, 2019 7:20 am
BTGmoderatorDC wrote:During a trip that they took together, Carmen, Juan, Maria, and Rafael drove an average (arithmetic mean) of 80 miles each. Carmen drove 72 miles, Juan drove 78 miles, and Maria drove 83 miles. How many miles did Rafael drive?

A. 80

B. 82

C. 85

D. 87

E. 89

OA D

Source: Official Guide
Let x = the number of miles Rafael drove

Average = 80
So, (72 + 78 + 83 + x)/4 = 80
Multiply both sides by 4 to get: 72 + 78 + 83 + x = 320
Simplify: 233 + x = 320
Solve: x = 87

Answer: D
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by swerve » Sat Apr 06, 2019 9:42 am
Total distance \(=\) average * number \(= 80*4= 320\)

So
\(C+J+R+M=320\cdots 72+78+R+83=320\)

\(R=320-233=87\)

Therefore, the correct answer is D
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