An alloy contains a mixture of two metals X and Y in the ratio of 2 : 3. The second alloy contains a mixture of the same metals, X and Y. in the ratio 7 : 3. In what ratio should the first and the second alloys be mixed so as to make a new alloy containing 50% of metal X?

What is compound interest accrued on an amount of Rs 45000 in 2 yr @ 9% per annum ? 

A vertical stick 12 cm long casts a shadow 8 cm long on the ground. At the same time, a tower casts a shadow 40 m long on the ground. The height of the tower is 

Directions:  The table given below presents the number of books on different subjects kept on separate shelves subjects with odd and even numbers are of arts and Science respectively

Find the ratio of S1: S7.

The perimeter of a triangle is equal to perimeter of a rectangle. Length of rectangle is 75% of side of a square and ratio of length to breadth of rectangle is 3 : 2. If difference between perimeter of square and that of rectangle is 36 cm, then find perimeter of triangle?

The average age of 30 students of a class is 15 years. A 20-year-old student left the class and replaced by two new students, whose age difference is 5 years. If the average age of all students is 15 years, then what will be ratio of young student to elder students. 

What will come in place of the question mark (?) in each of the following series?

 15     12    17  10     ?    8    21     6