What mathematical operation should come at the place of ‘?’ in the equation:
2 ? 6 – 12 ÷ 4 +2 =11.

A sum of money doubles itself at compound interest in 15 years. In how many years it  will become eight times?

In a school 80% of the students are girls. The number of boys are 500. Then the total number of students in the school is

Price of sugar rises by 20%. By how much percent should the consumption of sugar be reduced so that the expenditure does not change?

The radius of the circumcircle of a right-angled triangle is 15 cm and the radius of its in circle is 6 cm. Find the sides of the triangle. 

If A exceeds B by 40%, B is less than C by   20% , then A:C is

What sum will give Rs. 488 as the difference between simple interest and compound interest at 10% in $$ 1{1\over2}$$ years compounded half yearly ?

The maximum number of common tangents drawn to two circles when both the circles touch each other externally is