A number is doubled and 9 is added. If the resultant is tripled, it becomes 75. What is that number? 

The zeros of the cubic polynomial $$ {2x^{3}-x^{2}-2x+1}$$ are a, b and c respectively. Find ab + bc + ca =?

A rational number between $${3\over4} $$ and $${3\over8} $$ is :

Three numbers are such that if the average of any two of them is added to the third number, the sums obtained are 168, 174 and 180 respectively. What is the average of the original three numbers?

Direction : What value should come in the place of question mark (?) in the following questions?

11283 + 25 % of ? + 727 = 13280 

The difference between the greatest and least five-digit numbers formed by the digits 2,5,0,6,8 is (repetition of digits are not allowed) 

Direction : What value should come in place question mark(?) in the following questions?

$$2\over7$$ of $$ 5\over6$$ of ?=200

What will be remainder if (13)³ is subtracted from (66)² ?