Question

The mean of 30 observations is 60. The mean of first 20 observations is 65. Find the mean of last 10 observations.

Answer 1

Given:

Mean of 30 observations = 60

Mean of first 20 observations = 65

Step-wise calculation:

1. Total sum of 30 observations

= 30 × 60

= 1800

2. Sum of first 20 observations

= 20 × 65

= 1300

3. Sum of last 10 observations

= 1800 – 1300

= 500

4. Mean of last 10 observations

= 500 ÷ 10

= 50

The mean of the last 10 observations is 50.