BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

QANT Guide Q70

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 16
Joined: Mon Apr 15, 2013 3:32 pm

QANT Guide Q70

by cpay3245 » Fri May 10, 2013 9:46 pm
Need help in getting to the answer on this one!

List S consists of 10 consecutive ODD integers, and list T consists of 5 consecutive EVEN integers. If the least integer in S is 7 more than the least integer in T, how much greater is the average (arithmetic mean) of the integers in S than the average of integers in T?

a) 2
b) 7
c) 8
d) 12
e) 22
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 423
Joined: Fri Jun 11, 2010 7:59 am
Location: Seattle, WA
Thanked: 86 times
Followed by:2 members

by srcc25anu » Fri May 10, 2013 9:59 pm
Easiest approach is to try out with real numbers.
Least element of S = Least element of T + 7
Lets say least element of T = 2
Lets say least element of S = 2 + 7 = 9
T = {2,4,6,8,10} and Avg of T = 6
S = {9,11,13,15,17,19,21,23,25,27} and Avg of T = 18
Avg (T) - Avg (S) = 18 - 6 = 12
Ans D
Top
Junior | Next Rank: 30 Posts
Posts: 16
Joined: Mon Apr 15, 2013 3:32 pm

by cpay3245 » Fri May 10, 2013 10:56 pm
srcc25anu wrote:Easiest approach is to try out with real numbers.
Least element of S = Least element of T + 7
Lets say least element of T = 2
Lets say least element of S = 2 + 7 = 9
T = {2,4,6,8,10} and Avg of T = 6
S = {9,11,13,15,17,19,21,23,25,27} and Avg of T = 18
Avg (T) - Avg (S) = 18 - 6 = 12
Ans D
Thanks alot that is a great methond!
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 149
Joined: Wed May 01, 2013 10:37 pm
Thanked: 54 times
Followed by:9 members

by Atekihcan » Sat May 11, 2013 6:47 am
Average of S = (5th term + 6th term)/2
Average of T = 3rd term

Now, assume that smallest integer in S and T are s and t, respectively.
So, s = t + 7

Now, 5th and 6th term of S are (s + 8) and (s + 10)
So, average of S = (2s + 18)/2 = s + 9 = t + 16

And, 3rd term of T = t + 4

Difference in average = (t + 16) - (t + 4) = 12

Answer : D
Top
Post new topic Post Reply
• Page 1 of 1