The mean of 10 observations was calculated as 40. It was detected on rechecking that the value of 45 was wrongly copied as 15. Find the correct mean.

Solution:

Given, the mean of 10 observations was calculated as 40.

It was detected on rechecking that the value of 45 was wrongly copied as 15.

We have to find the correct mean.

We know, Mean = Sum of all observations/Number of observations

Number of observations = 10

Mean = 40

Now, 40 = sum of all observations/10

Sum of all observations = 10(40)

Incorrect sum = 400

Incorrect observation = 15

Correct observation = 45

Correct sum = Incorrect sum - incorrect observation + correct observation

= 400 - 15 + 45

= 400 + 30

= 430

Correct mean = correct sum / number of observation

= 430/10

= 43

Therefore, the correct mean is 43.

✦ Try This: The mean of 12 observations was calculated as 50. It was detected on rechecking that the value of 35 was wrongly copied as 65. Find the correct mean.

☛ Also Check: NCERT Solutions for Class 7 Maths Chapter 3

---

NCERT Exemplar Class 7 Maths Chapter 3 Sample Problem 13

The mean of 10 observations was calculated as 40. It was detected on rechecking that the value of 45 was wrongly copied as 15. Find the correct mean.

Summary:

The mean of 10 observations was calculated as 40. It was detected on rechecking that the value of 45 was wrongly copied as 15. The correct mean is 43.

---

☛ Related Questions:

• The median of observations 11, 12, 14, 18, x + 2, 20, 22, 25, 61 arranged in ascending order is 21. . . . .
• Study the double bar graph given below and answer the questions that follow: (a) What information do . . . .
• The following double bar graph represents test matches results summary for Cricket Team of country X . . . .