A number equal to 4 times of the mean and a frequency equal to k is inserted in the data of n observations. If the new mean is 7 5 times the old mean, then n k is equal to

Question

A number equal to 4 times of the mean and a frequency equal to k is inserted in the data of n observations. If the new mean is 7 5 times the old mean, then n k is equal to,

MARKS App · Accepted Answer

x - n e w = 7 5 x - From the given information, x - n e w = n x - + 4 k x - n + k = 7 5 x - ⇒ 5 n + 20 k = 7 n + 7 k ⇒ 13 k = 2 n ⇒ n k = 13 2

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