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03 Mar 2020, 03:40
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C
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Difficulty:
35%
(medium)
Question Stats:
69% (01:54) correct
31%
(01:30)
wrong
based on 60
sessions
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What was the average money with the class of 50 students whose roll numbers are from 1 to 50?
(1) The average money with the first 25 students of the class is $25 more than the average money with the last 25 students.
(2) The average money with the first 25 students is twice the average money with the last 25 students.
(1) The average money with the first 25 students of the class is $25 more than the average money with the last 25 students.
(2) The average money with the first 25 students is twice the average money with the last 25 students.
03 Mar 2020, 10:03
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Bunuel
find avg money with class of 50 from 1 to 50 roll no
#1
The average money with the first 25 students of the class is $25 more than the average money with the last 25 students.
sum of money ( from 1 to 25 ) / 25 = 25 + sum of money from ( 26 to 50) /25
let sum of money ( from 1 to 25 ) = X
and sum of money from ( 26 to 50) /25= Y
we get
X = 625+Y
insufficient
#2
The average money with the first 25 students is twice the average money with the last 25 students
we can say
X = 2*Y
insufficient
from 1 &2
we get
2*Y=625+Y
Y = 625
so X = 1250
so total avg ; 1250+625 ; 1875
IMO C sufficient
shameekv1989
03 Mar 2020, 10:21
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Bunuel
We can use the weighted average concept.
last 50% students have an average of x
first 50% have an average of x+25
\(\frac{(x+25)}{2} +\frac{ x}{2} = Total Average = \frac{(2x+25)}{2}\) - Not Sufficient
last 50% students have an average of x
first 50% have an average of 2x
\(Total average = \frac{2x}{2} + \frac{x}{2} = \frac{3x}{2}\)
From i) and ii) we get \(\frac{3x}{2} = \frac{(2x+25)}{2} \) => \(x=25\)
\(Total average = \frac{3x}{2} = 37.5 \)
Answer - C
