The average (arithmetic mean) amount of money that a group of four fri

Question

The average (arithmetic mean) amount of money that a group of four friends pays for rent each month is $800. After one person’s rent is increased by 20 percent the new average rent is $850. What was the original rent of the friend whose monthly rent increased?

A. $800
B. $900
C. $1,000
D. $1,100
E. $1,200

A. $800
B. $900
C. $1,000
D. $1,100
E. $1,200

globaldesi · Answer

let four friends be 
a, b, c, d
given a+b+c+d = 800*4= 3200 -------------(eq 1)
also given 
1.2 a +b+c+d = 850*4 = 3400 --------------(eq 2)

sub 1 from 2

gives
.2 a = 200
or a = 1000
hence C

ScottTargetTestPrep · Answer

The total rent paid by the four friends is 800 x 4 = 3200. Letting x = the old rent paid by the individual whose rent increased, we subtract his old rent of x and replace it with his new rent of 1.2x. Then we calculate the new average with the equation:

(3200 - x + 1.2x) / 4 = 850

3200 + 0.2x = 3,400

0.2x = 200

x = 1,000

Answer: C

Manasvi1 · Answer

Let the rent of all four friends be a,b,c,d

Then,  \frac{a + b + c + d }{ 4}  = 800

=> a + b + c + d = 800 * 4 = 3200 .....(i)

Given, rent of one person increases by 20%

Suppose rent of A increases. Then,

Rent of A = a + 20% of a = a +  \frac{a}{5}  =  \frac{6a}{5}  = 1.2 a

So,  \frac{ 1.2 a + b + c + d}{4}  = 850

=> 1.2 a + b + c + d = 3400

=> b + c + d = 3400 - 1.2 a

Putting value of ( b + c + d ) in ( i ) we get,

a + 3400 - 1.2 a = 3200
=> a + 3400 = 3200 - 1.2 a
=> 0.2 a = 200
= > a =  \frac{200}{0.2}  = 1000

So original rent = 1000
 Hence OA(C)

Abhishek009 · Answer

\frac{800 + 800 + 800 + 800}{4} = 800

\frac{1000 + 800 + 800 + 800}{4} = 850

Hence, Answer must be (C)

TheNightKing · Answer

Original Total = 3200

New Total = 3400.

We know that 200 increase is due to 20% increase of one person's rent. But since 200 represents 20% increase that means the original rent was 1000$.

Answer C

The average (arithmetic mean) amount of money that a group of four fri

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The average (arithmetic mean) amount of money that a group of four fri

Prep Toolkit

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