The angle of elevation of an aeroplane from a point on the ground is 60°. After flying for 15 second, the angle of elevation changes to 30°. If the Aeroplane is flying at a height of 4500 meter, then what is the speed (in m/s) of aeroplane?

Find the difference between compound interest and simple interest on 5000 for 2 years at 8% p.a payable annually.

The sum of two digit number is 16. If the digit is interchanged the number is formed 18 less than the original number. Find the original number.

A family has two grandparents, two parents and four children. Two years ago, the average age of grandparents was 72 years. A year ago, the average age of parents was 36 years. Currently, the average age of children is 12 years. What is the current average age of the family?

The following penalty diagram shows the 4 year exam results of the students of 10th standard. Study the diagram and answer the following questions.

What is the ratio of the total students who have attained second division in the year 2000 and appeared in the examination?

The single discount which is equivalent to three successive discounts of 25%, 20% and 10% is-

A man gives 20% of his money to his eldest son, 30% of remaining he gives to his younger son. 10% of the remaining he gives in a school for poor boys still he has Rs.100.80. Find his total sum. 

What will be the area (cm²) of the curved surface of an elliptical cylinder whose height and diameter are 10 cm and 8 cm respectively?