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UPSC NDA I 2021 Mathematics Solved Paper
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© examsnet.com
Question : 67
Total: 120
The mean of 12 observations is 75 . If two observation are discarded, then the mean of the remaining observations is
65
.
What is the mean of the discarded observations?
[NDA-I 2021]
250
125
120
Cannot be determined due to insufficient data
Validate
Solution:
👈: Video Solution
Calculation:
Let the discarded values be
x
and
y
,
Sum of all the 12 values
=
12
×
mean
S
1
=
12
×
75
=
900
Sum of the 10 values after discarding
=
10
×
new mean
S
2
=
10
×
65
=
650
Now
650
+
x
+
y
=
900
x
+
y
=
900
−
650
=
250
Average of
x
and
y
=
x
+
y
2
Average
=
250
2
=
125
© examsnet.com
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