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Difficulty:
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Question Stats:
89% (01:10) correct
11%
(01:33)
wrong
based on 274
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The average (arithmetic mean) of 9 scores is N. If a 10th score is then included with the original 9, the average of the 10 scores is T. Which of the following expressions represents the value of the 10th score?
(A) \(10(T - N)\)
(B) \(10T - 9N\)
(C) \(\frac{10T - 9N}{10}\)
(D) \(\frac{10T - 9N}{9}\)
(E) \(\frac{10T - 9N}{2}\)
(A) \(10(T - N)\)
(B) \(10T - 9N\)
(C) \(\frac{10T - 9N}{10}\)
(D) \(\frac{10T - 9N}{9}\)
(E) \(\frac{10T - 9N}{2}\)
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manavivarma
Joined: 06 Oct 2018
Last visit: 23 Mar 2019
Posts: 16
Given Kudos: 6
Location: Oman
Concentration: Marketing, General Management
Schools: Kellogg '21 Duke '21 Stanford '21 CBS '21
GMAT 1: 710 Q49 V38
GPA: 3.33
WE:Public Relations (Advertising and PR)
Updated on: 30 Oct 2018, 01:17
Originally posted by manavivarma on 30 Oct 2018, 01:13.
Last edited by manavivarma on 30 Oct 2018, 01:17, edited 1 time in total.
Last edited by manavivarma on 30 Oct 2018, 01:17, edited 1 time in total.
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The average of the nine numbers is given by \(\frac{a1+a2+a3+...+a9}{9}=N\).
Therefore, \(a1+a2+a3...+a9= 9N\). (Let this be equation 1)
Now the average of the nine numbers and an added 10th number is given=T.
9
Therefore \(\frac{a1+a2+a3+...+a9+a10}{10}=T\) (Let this be equation 2)
From equation 1, we can substitute a1+a2+...a9 with 9N in equation 2; giving us:
\(\frac{9N+a10}{10}=T.\)
Therefore, \(a10=10T-9N\) (Choice B)
Therefore, \(a1+a2+a3...+a9= 9N\). (Let this be equation 1)
Now the average of the nine numbers and an added 10th number is given=T.
9
Therefore \(\frac{a1+a2+a3+...+a9+a10}{10}=T\) (Let this be equation 2)
From equation 1, we can substitute a1+a2+...a9 with 9N in equation 2; giving us:
\(\frac{9N+a10}{10}=T.\)
Therefore, \(a10=10T-9N\) (Choice B)
30 Oct 2018, 01:16
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Sum initially=9*N
Sum finally=9N+x where x is the 10th term
Given,
(9N+x)/10=T
So, x=10T-9N
B should be the correct choice
Sent from my Redmi Note 3 using GMAT Club Forum mobile app
Sum finally=9N+x where x is the 10th term
Given,
(9N+x)/10=T
So, x=10T-9N
B should be the correct choice
Sent from my Redmi Note 3 using GMAT Club Forum mobile app
