Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

It is currently 15 Jul 2019, 23:20

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

If a + 2c = 8, b + 5c = 13, and 3a + 4b= 50, what is the average (arit

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56233
If a + 2c = 8, b + 5c = 13, and 3a + 4b= 50, what is the average (arit  [#permalink]

Show Tags

New post 02 Jan 2018, 01:31
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

80% (02:34) correct 20% (02:56) wrong based on 118 sessions

HideShow timer Statistics


SVP
SVP
User avatar
V
Status: It's near - I can see.
Joined: 13 Apr 2013
Posts: 1685
Location: India
Concentration: International Business, Operations
Schools: INSEAD Jan '19
GPA: 3.01
WE: Engineering (Real Estate)
Reviews Badge
Re: If a + 2c = 8, b + 5c = 13, and 3a + 4b= 50, what is the average (arit  [#permalink]

Show Tags

New post 02 Jan 2018, 04:51
1
Bunuel wrote:
If a + 2c = 8, b + 5c = 13, and 3a + 4b= 50, what is the average (arithmetic mean) of a, b, and c?

A. 3
B. 4
C. 5
D. 6
E. 7


a + 2c = 8 ----> a = 8 - 2c ----->(I)
b + 5c = 13 -----> b = 13 - 5c ------> (II)

Use the values of a & b in 3a + 4b = 50

3 (8 - 2c) + 4 (13 - 5c) = 50

24 - 6c + 52 - 20c = 50

-26c = 50 - 76

c = 1

We can calculate b = 8 & a = 6

Average = \(\frac{(6 + 8 + 1)}{3}\) = 5

(C)
_________________
"Do not watch clock; Do what it does. KEEP GOING."
Intern
Intern
avatar
B
Joined: 10 Jun 2018
Posts: 13
CAT Tests
Re: If a + 2c = 8, b + 5c = 13, and 3a + 4b= 50, what is the average (arit  [#permalink]

Show Tags

New post 04 Jan 2019, 21:46
Answer C

1. a+2c=8
2. b+5c=13
3. 3a+4b=50

Multiply equation 1. by 5 and equation 2. by 2 to cancel out c. After multiplying, equation 1. becomes 5a+10c=40
and equation 2. becomes 2b+10c=26
Subtracting these 2 equations: 5a-2b=14 .........(equation A)
Now we have 2 equations to solve:
A) 5a-2b=14
3. 3a+4b=50

Multiply equation A by 2 to equalize b and then add the two equations to give the value of a. Substitute the value of a in earlier equations to find value of b and c. The values are:
a= 6, b=8, c=1

Mean = (a+b+c)/3 = 15/3= 5
GMAT Club Bot
Re: If a + 2c = 8, b + 5c = 13, and 3a + 4b= 50, what is the average (arit   [#permalink] 04 Jan 2019, 21:46
Display posts from previous: Sort by

If a + 2c = 8, b + 5c = 13, and 3a + 4b= 50, what is the average (arit

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne