In a series of tests, A appeared for 8 tests. Each test was marked out of 30 and averages 25. However, while checking his files, A could only find 7 of the 8 tests. For these he scored 29, 26, 18, 20, 27, 24 and 29. Determine how many marks he scored for the eighth test.

Find the mean of 8, 12, 16, 22, 10 and 4. Find the resulting mean, if each of the observations, given above, be :

(i) multiplied by 3.

(ii) divided by 2.

(iii) multiplied by 3 and then divided by 2.

(iv) increased by 25 %.

(v) decreased by 40 %.

The mean of 6 numbers is 42. If one number is excluded, the mean of remaining numbers is 45. Find the excluded number.

The mean of 10 numbers is 24. If one more number is included, the new mean is 25. Find the included number.