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30 students had an average of X, while 20 students had an average of

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Math Expert
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30 students had an average of X, while 20 students had an average of  [#permalink]

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New post 01 Mar 2018, 00:39
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

83% (01:26) correct 17% (01:13) wrong based on 34 sessions

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Re: 30 students had an average of X, while 20 students had an average of  [#permalink]

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New post 01 Mar 2018, 00:52
Bunuel wrote:
30 students had an average of X, while 20 students had an average of 80. What is the average for the entire group?

(A) (X + 80)/50
(B) (X + 80)/2
(C) 50/(X + 80)
(D) 3X/5 + 32
(E) (30X + 80)/50


Instead of calculating, we'll pick an easy number for X.
This is an Alternative appraoch.

Say X = 80.
Then all students had an average of 80 so the total average must also be 80.
(A) is not 80.
(B) is 80. Maybe. Let's check the others.
(C) is not 80.
(D) is 240/5 + 32 = 48 + 32 = 80.
(E) is (3*80+8)/5 = 248/5 which is not 80.

So our answer is (B) or (D).
Let's now try X = 0. Then the average is (20*80)/50 = 160/5 = 32
(B) is 40. No!
(D) is 0 + 32 = 32 and is our answer.

(D) is our answer.
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Re: 30 students had an average of X, while 20 students had an average of  [#permalink]

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New post 01 Mar 2018, 03:39
Bunuel wrote:
30 students had an average of X, while 20 students had an average of 80. What is the average for the entire group?

(A) (X + 80)/50
(B) (X + 80)/2
(C) 50/(X + 80)
(D) 3X/5 + 32
(E) (30X + 80)/50


we are looking for the average of the entire group.
first of all i want to dig up a issue that our total student is 30+20=50

now , total no. of 30 students is 30x
total no. of 20 students is 20*80=1600

average of 50 students = 30x+1600/50
= 30x/50+1600/50
=3x/5+32
so, option D is our correct answer. hope it helps u.
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Re: 30 students had an average of X, while 20 students had an average of  [#permalink]

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New post 01 Mar 2018, 05:45
To find the average score,
total score for 30 students is 30x
Total score for 20 students is (20*80=1600)
Average score for group(30+20=50)
is (30x + 1600)/50
That is
(3x/5)+32

Option D



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Re: 30 students had an average of X, while 20 students had an average of  [#permalink]

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New post 01 Mar 2018, 05:46
selim wrote:
Bunuel wrote:
30 students had an average of X, while 20 students had an average of 80. What is the average for the entire group?

(A) (X + 80)/50
(B) (X + 80)/2
(C) 50/(X + 80)
(D) 3X/5 + 32
(E) (30X + 80)/50


we are looking for the average of the entire group.
first of all i want to dig up a issue that our total student is 30+20=50

now , total no. of 30 students is 30x
total no. of 20 students is 20*80=1600

average of 50 students = 30x+1600/50
= 30x/50+1600/50
=3x/5+32
so, option D is our correct answer. hope it helps u.
U have to calculate sir... Cos of time

Sent from my [device_name] using [url]GMAT Club Forum mobile app[/url]
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Re: 30 students had an average of X, while 20 students had an average of  [#permalink]

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New post 02 Mar 2018, 10:35
Bunuel wrote:
30 students had an average of X, while 20 students had an average of 80. What is the average for the entire group?

(A) (X + 80)/50
(B) (X + 80)/2
(C) 50/(X + 80)
(D) 3X/5 + 32
(E) (30X + 80)/50


The average for the entire group is:

(30X + 20(80))/50 = (30X + 1600)/50 = 30X/50 + 1600/50 = 3X/5 + 32

Answer: D
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Re: 30 students had an average of X, while 20 students had an average of  [#permalink]

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New post 02 Mar 2018, 10:57
Bunuel wrote:
30 students had an average of X, while 20 students had an average of 80. What is the average for the entire group?

(A) (X + 80)/50
(B) (X + 80)/2
(C) 50/(X + 80)
(D) 3X/5 + 32
(E) (30X + 80)/50



Average of the entire group= 30X+1600/(30+20)=30X+1600/50=3X/5+32
Answer D
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Re: 30 students had an average of X, while 20 students had an average of   [#permalink] 02 Mar 2018, 10:57
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