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From a group of 12 students with average weight being 72.5 kgs, two st 31 Dec 2019, 03:09
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B
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35% (medium)

Question Stats:

70% (02:13) correct 30% (01:58) wrong based on 53 sessions

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From a group of 12 students with average weight being 72.5 kgs, two students leave. Because the two leave, the average of the group falls to 71.25 kgs. Find the average weight of the two students who leave the group.

A. 78.5
B. 78.75
C. 79.25
D. 157
E. 157.5
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B
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From a group of 12 students with average weight being 72.5 kgs, two st 31 Dec 2019, 11:17
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Bunuel
From a group of 12 students with average weight being 72.5 kgs, two students leave. Because the two leave, the average of the group falls to 71.25 kgs. Find the average weight of the two students who leave the group.

A. 78.5
B. 78.75
C. 79.25
D. 157
E. 157.5
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from given info
12*72.5- 712.5 = 157.5
157.5 = 78.75
IMO B
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From a group of 12 students with average weight being 72.5 kgs, two st 31 Dec 2019, 13:03
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As we have 12 students, the total weight for all those 12 students is \(72,5*12 = 870 kgs\).
If 2 students leave and we have a new total weight average of \(71,25\), this means that the total weight is now \(71,25*10=712,5\)

Consequently, the sum of weights of the the two students which left was \(870-712,5=157,5\)
The average will be \(157,5/2=78,75\)

Option B
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From a group of 12 students with average weight being 72.5 kgs, two st 31 Dec 2019, 16:37
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Solution



Given
    • From a group of 12 students with average weight being 72.5 kgs, two students leave.
    • Hence, the average of the group falls to 71.25 kgs

To find
    • The average weight of the two students who leave the group.

Approach and Working out

Let the average weight of the students who leave the group =x
    • 72.5 *12 -2x /10 =71.25
    • 72.5*12 -2x=71.25 *10
    • 2x = 72.5 *12 – 71.25 *10
    • x = 72.5 *6 -71.25 *5
    • x =72.5 * (5+1) -71.25 *5
    • x =5*1.25 +72.5
    • x = 6.25 +72.5 =78.75

Thus, option B is the correct answer.
Correct Answer: Option B
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From a group of 12 students with average weight being 72.5 kgs, two st 31 Dec 2019, 22:33
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Given that
Number of students = 12
Average wight = 72.50
Total Wight = (70+ 2+ 1/2)* 12= 840 + 24 + 6 = 870

After leaving 2 persons, remaining number = 10
Total = (71.25) (70+1+1/4)*10
= 700 + 10 + 2.5
= 712.50

Total wight of 2 persons = 870 - 712.50
= 157.50
Average wight = 157.50/2
= 78.75(B)
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