₹ 180 contained in a box consists of one rupee, 50 paise and 25 paise coins in the ratio 2 : 3 : 4 . What is the number of 50 paise coins?

A principal increases by 21% over 2 years with compound interest. What will be the simple interest in 4 years at the same interest rate of Rs 1000?

The perimeter of rectangle of length 2 (x + 3) cm and breadth 2 (x + 1) cm is double the perimeter of a square of area 225 cm². Find the area of rectangle.

If the graph of the equations x + y = 0 and 5y + 7x =24 intersect at (m, n), then the value of m + n is :

The graph of the equations 25x + 75y = 225 and x = 9 meet the point: 

The average of 10 numbers is calculated as 15. It is discovered later on that while calculating the average one number, namely 36, was wrongly read as 26. The correct average is: