1) 23, ?,53, 163, 657, 3291

2) 187, 17, 119, 23.8, ?, 35.7

3) 117, 174, 254, 361, 499, ?

4) 7, 4.5, 7.5, 16.25, 39.5, ?, 334.25

5) 42, 45, 57, 87, 143, ? , 369

6) In a certain examination, the average mark of an examinee is 64 per paper. If he had obtained 18 more marks for his mathematics paper and 4 more marks for his science paper, his average per paper would have been 66. How many papers were there in the examination?

7) The average age of a man and his two twin sons born on the same day is 30 years. The ratio of the ages of father and one son is 5: 2, what is the age of father?

8) 35% of a number is two times 75% of another number. What is the ratio between the first and the second number?

9)If a certain sum at compound interest becomes double in 5 year, then in how many years, it will be 16 times at the same rate of interest?

10) If the difference between the simple interest and compound interest on some amount at 20% pa for 3 years is 48, then what must be the principal amount?