Question

While checking the value of 20 observations, it was noted that 125 was wrongly noted as 25 while calculating the mean and then the mean was 60. Find the correct mean

Answer 1

Let y be the sum of observation of 19 (20 – 1) numbers leaving 125,

So, y + 25 = 20 × 60 = 1200 (Mean = sum of observations/ no. of observations)

As we know,

x+25=20×60=1200

Also

x+125=20×y=20y

Next, Subtract 125−25=20y−1200

20y=1300

y=65

Answer 2

Let y be the sum of observation of 19 (20 - 1) numbers leaving 125,

So, y + 25 = 20 * 60 = 1200

(Mean = sum of observations/ no. of observations)

As we know

➠ x + 25 = 20 × 60 = 1200

Also

➠ x + 125 =20 × y = 20y

Next, Subtract 125 - 25 = 20y - 1200

➠ 20y = 1300

➠ y = 65

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