On the most recent test in stats class, Jamal scored x point

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BTGmoderatorDC: Moderator; Posts: 7187; Joined: Thu Sep 07, 2017 4:43 pm; Followed by:23 members

On the most recent test in stats class, Jamal scored x point

by BTGmoderatorDC » Sun Dec 23, 2018 2:05 pm

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On the most recent test in stats class, Jamal scored x points and Raya scored 73 points. If the average of Cliff and Raya`s scores is 79 points, and the average of Jamal and Cliff`s scores is 89, then x =

A. 73
B. 79
C. 89
D. 93
E. 97

OA D

Source: Princeton Review

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Source: Beat The GMAT — Problem Solving | Sun Dec 23, 2018 2:05 pm

fskilnik@GMATH: GMAT Instructor; Posts: 1449; Joined: Sat Oct 09, 2010 2:16 pm; Thanked: 59 times; Followed by:33 members

by fskilnik@GMATH » Sun Dec 23, 2018 5:03 pm

BTGmoderatorDC wrote:On the most recent test in stats class, Jamal scored x points and Raya scored 73 points. If the average of Cliff and Raya`s scores is 79 points, and the average of Jamal and Cliff`s scores is 89, then x =

A. 73
B. 79
C. 89
D. 93
E. 97
Source: Princeton Review

$$? = x$$
$$\left\{ \matrix{
2 \cdot 89 = J + C = x + C \hfill \cr
2 \cdot 79 = R + C = 73 + C \hfill \cr} \right.\,\,\,\,\,\mathop \Rightarrow \limits^{\left( - \right)} \,\,\,\,\,2 \cdot \left( {89 - 79} \right) = x - 73$$
$$? = 73 + 20 = 93\,\,\,\,\, \Rightarrow \,\,\,\,\,\left( {\rm{D}} \right)$$

This solution follows the notations and rationale taught in the GMATH method.

Regards,
Fabio.

Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
English-speakers :: https://www.gmath.net
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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Fri Feb 15, 2019 5:22 pm

BTGmoderatorDC wrote:On the most recent test in stats class, Jamal scored x points and Raya scored 73 points. If the average of Cliff and Raya`s scores is 79 points, and the average of Jamal and Cliff`s scores is 89, then x =

A. 73
B. 79
C. 89
D. 93
E. 97

OA D

Source: Princeton Review

Letting c = Cliff's score, we can create the equation:

(c + 73)/2 = 79

c + 73 = 158

c = 85

Since the average of Cliff and Jamal's scores is 89:

(x + 85)/2 = 89

x + 85 = 178

x = 93

Answer: D

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