**331. The average of first five prime numbers greater than 20 is____________?**

A. 31.00

B. 31.01

C. 32.00**D. 32.2**

**332. The average of 9 observations was 9, that of the 1st of 5 being 10 and that of the last 5 being 8. What was the 5th observation?****A. 9**

B. 8

C. 7

D. 6

**333. The average of 1st 3 of 4 numbers is 16 and of the last 3 are 15. If the sum of the first and the last number is 13. What is the last numbers?**

A. 8

B. 6**C. 5**

D. 2

**334. The average age of three boys is 15 years and their ages are in proportion 3:5:7. What is the age in years of the youngest boy?**

A. 15**B. 9**

C. 18

D. 21

**335. The average of first 10 odd numbers is_____________?**

A. 11**B. 10**

C. 12

D. 17

**336. The average of first 10 natural numbers is____________?**

A. 5**B. 5.5**

C. 6.5

D. 6

**337. The average of first ten prime numbers which are odd is____________?**

A. 12.9

B. 13.8**C. 15.8**

D. 17

**338. The average of 11 numbers is 10.9. If the average of first six is 10.5 and that of the last six is 11.4 the sixth number is_____________?**

A. 11.0

B. 11.3

C. 11.4**D. 11.5**

**339. The average of first 10 even numbers is___________?**

A. 18

B. 22

C. 9**D. 11**

**340. The average salary of workers in an industry is Rs.200 the average salary of technicians being Rs.400 and that of non-technicians being Rs.125. What is the total number of workers?**

A. 250

B. 275**C. 550**

D. 400