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The average (arithmetic mean) of 10, 30, and 50 is 5 more

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The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

Practice Questions
Question: 53
Page: 159
Difficulty: 600


GMAT Club is introducing a new project: The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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SOLUTION

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

The average of 10, 30, and 50 is \(\frac{10+30+50}{3}=30\).

The average of 20, 40 and x must be 30-5=25, so the sum of these 3 numbers must be 3*25=75 --> 20+40+x=75 --> x=15.

Answer: A.
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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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New post 01 Oct 2012, 05:29
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The average of 10 30 50 is \(\frac{A = 10+30+50}{3}\) \(= 30\)
The second Average must be 5 less : 25. Using common sense or back solve we can obtain the solution.

Starting with A because we need a small value in the difference.

So,\(\frac{A = 20+40+15}{3}\) \(= 25\)

A is the answer

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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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New post 01 Oct 2012, 19:47
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The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and
(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

Average of 10,30,50 = 30
Average of 20,40 & x = 25
so 60 + x = 75----> x = 15
Answer A
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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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New post 04 Oct 2012, 00:47
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Answer is A (15)

Since 10, 30 and 50 are numbers in equally spaced sets, average is 30

Now 30 is 5 greater than 25 ....Thus average of 20, 40 and (x) is 25 ......This implies, sum of 3 numbers should be 75 to make the average = 25

Thus, answer is 15 = 75 - 20 - 40
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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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New post 04 Oct 2012, 14:05
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SOLUTION

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

The average of 10, 30, and 50 is \(\frac{10+30+50}{3}=30\).

The average of 20, 40 and x must be 30-5=25, so the sum of these 3 numbers must be 3*25=75 --> 20+40+x=75 --> x=15.

Answer: A.

Kudos points given to everyone with correct solution. Let me know if I missed someone.
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Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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New post 10 Sep 2014, 19:08
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55

Practice Questions
Question: 53
Page: 159
Difficulty: 600


GMAT Club is introducing a new project: The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide for GMAT® Review, 13th Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
1. Please provide your solutions to the questions;
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!




10+30+50 = 90

90/3=30.

so mean of 20+40+x should be 25...

25*3=75(total),

60+x=75

x=15.
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The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55


Algebraic Method (Forming single equation for result)

\(\frac{10 + 30 + 50}{3} = \frac{20 + 40 + x}{3} + 5\)

x = 15

Shortcut (By observation) Method

10, 30, 50 are equally spaced; so average = 30

For the other set, required average would be 30 - 5 = 25

It means total = 75

Required number = 75 - (20+40) = 15
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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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New post 01 Oct 2015, 21:29
Hello from the GMAT Club BumpBot!

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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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New post 30 May 2016, 05:24
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55


Let’s first determine the average of 10, 30, and 50, using the average formula.

average = sum/quantity

average = (10+30+50)/3

average = 90/3

average = 30

We can now rephrase the question to ask: "30 is 5 more than the average of 20, 40, and what value?" Let’s label the missing value as n and create an equation.

30 = (20+40+n)/3 + 5

25 = (20+40+n)/3

75 = 60 + n

15 = n

The answer is A.
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Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more [#permalink]

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New post 30 May 2016, 06:15
[quote="Bunuel"]The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

The average (arithmetic mean) of 10, 30, and 50 is 5 more than the average of 20, 40, and

(A) 15
(B) 25
(C) 35
(D) 45
(E) 55
/quote]

avg of (10, 30, 50) = (10+30+50)/ 3 = 30.

Avg of next set = 25.

There are 3 nos. So sum of those 3 nos. = 25 * 3 = 75.
Third number = 75 - 20-40 = 15

(A) is the answer.
Re: The average (arithmetic mean) of 10, 30, and 50 is 5 more   [#permalink] 30 May 2016, 06:15
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