RRB NTPC Mains or Stage 2 Model Paper 7 with solutions

Question : 14 of 120

Marks: +1, -0

The mean of 100 values is 45. If 15 is added to each of the first forty values and 5 is subtracted from each of the remaining sixty values, the new mean becomes

Validate

Solution:

(b) Given that, mean of 100 values is 45
∴ Sum of 100 values, i.e.

Σ↙{i=l}↖{100}

x= 45 × 100

(a)ccording to condition,

Σ↙{i=1}↖{40}x _i+15 ×40 +Σ↙{i=14}↖{100}x_i -5 × 60

[Σ↙{i=1}↖{40}+Σ↙{i=14}↖{100}x_i]+600-300

Σ↙{i=1}↖{100}x_i+300

= 4500 + 300 = 4800 [from equation (i)]
∴ New mean =

4800/100= 48

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