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# The average (arithmetic mean) of the five numbers x, 91, 120, 134, and

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Joined: 26 Apr 2018
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The average (arithmetic mean) of the five numbers x, 91, 120, 134, and  [#permalink]

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Updated on: 30 Jul 2018, 01:40
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Difficulty:

25% (medium)

Question Stats:

67% (00:56) correct 33% (01:03) wrong based on 82 sessions

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The average (arithmetic mean) of the five numbers x, 91, 120, 134, and 220 is what percent of the sum of the five numbers?

(A) 20%
(B) 22%
(C) 25%
(D) 30%
(E) It cannot be determined from the information given.

Originally posted by bettatantalo on 30 Jul 2018, 01:24.
Last edited by Bunuel on 30 Jul 2018, 01:40, edited 1 time in total.
Renamed the topic, edited the question, added the OA and moved to PS forum.
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Re: The average (arithmetic mean) of the five numbers x, 91, 120, 134, and  [#permalink]

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30 Jul 2018, 01:43
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1
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bettatantalo wrote:
The average (arithmetic mean) of the five numbers x, 91, 120, 134, and 220 is what percent of the sum of the five numbers?

(A) 20%
(B) 22%
(C) 25%
(D) 30%
(E) It cannot be determined from the information given.

The average of five numbers = (sum of the numbers)/5. So, the average of five numbers is 1/5, or 20% of the sum.

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The average (arithmetic mean) of the five numbers x, 91, 120, 134, and  [#permalink]

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30 Jul 2018, 21:45
bettatantalo wrote:
The average (arithmetic mean) of the five numbers x, 91, 120, 134, and 220 is what percent of the sum of the five numbers?

(A) 20%
(B) 22%
(C) 25%
(D) 30%
(E) It cannot be determined from the information given.

You can either think logically and immediately choose the choice A or do algebraically and see the same result. In both cases, the logic plays a monumental role in this problem.

Finding Average: $$\frac{x+565}{5}$$

[b]The Sum
x+565

The Sum is the total and the average is the part, so you can create an equation: $$\frac{x+565}{5}$$ / x+565 = $$\frac{y%}{100%}$$
You can see that we have two variables x and y, but have only one equation. So, algebraically it's somehow impossible to find x and y. But you also can notice that you divide the numerator of the first fraction into 5, which in percent form is 100/5 yields 20%.
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The average (arithmetic mean) of the five numbers x, 91, 120, 134, and  [#permalink]

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30 Jul 2018, 22:55
1

Solution

Given:
• We are given 5 numbers: x, 91, 120, 134, and 220

To find:
• Arithmetic mean of : x, 91, 120, 134, and 220 is what percent of the sum of the five numbers

Approach and Working:

$$Average= \frac{Sum\ of\ the\ five\ numbers}{5}$$

Method:1

Hence, Average if $$\frac{1}{5}$$ of sum of the five numbers.
Thus, average is 20% of sum of the five number.

Method:2

• To convert average to percentage, we can multiply by 100.
• Average= Sum of the five numbers/5 *100%= Average= 20% of Sum of the five numbers

Hence, the correct answer is option A.

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Re: The average (arithmetic mean) of the five numbers x, 91, 120, 134, and  [#permalink]

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12 Sep 2018, 07:13
1
bettatantalo wrote:
The average (arithmetic mean) of the five numbers x, 91, 120, 134, and 220 is what percent of the sum of the five numbers?

(A) 20%
(B) 22%
(C) 25%
(D) 30%
(E) It cannot be determined from the information given.

OA: A

$$Average = \frac{Sum\quad of \quad Elements}{Number \quad of \quad Elements}$$

$$\frac{Average}{Sum\quad of \quad Elements} =\frac{1}{Number \quad of \quad Elements}$$

Multiplying by 100 on both sides, we get

$$\frac{Average}{Sum\quad of \quad Elements}*100 =\frac{1}{Number \quad of \quad Elements} * 100$$

$$Number \quad of \quad Elements=5$$

$$\frac{Average}{Sum\quad of \quad Elements}*100 =\frac{1}{5}*100=20$$
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Re: The average (arithmetic mean) of the five numbers x, 91, 120, 134, and  [#permalink]

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14 Sep 2018, 08:00
bettatantalo wrote:
The average (arithmetic mean) of the five numbers x, 91, 120, 134, and 220 is what percent of the sum of the five numbers?

(A) 20%
(B) 22%
(C) 25%
(D) 30%
(E) It cannot be determined from the information given.

The average of x, 91, 120, 134, and 220 is:

(x + 91 + 120 + 134 + 220)/5

The sum is:

x + 91 + 120 + 134 + 220

So the average as a percent of the sum is:

[(x + 91 + 120 + 134 + 220)/5]/(x + 91 + 120 + 134 + 220) = 1/5 = 20%

Alternate solution:

Since sum = average x quantity, the average is 1/quantity x 100 percent of the sum. Since here we have 5 numbers, the average is 1/5 x 100 = 20 percent of the sum.

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Re: The average (arithmetic mean) of the five numbers x, 91, 120, 134, and &nbs [#permalink] 14 Sep 2018, 08:00
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# The average (arithmetic mean) of the five numbers x, 91, 120, 134, and

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