Solve the following equation.

A number, on subtracting 15 from it reduces to its 80 %. What is 40 % of the number? 

There are 80 students in a class out of these 15% are girls. The monthly fee of each girl is Rs.350 and monthly fee of each boy is 38% more than each girl. What is the total fee of girls and boys in the class?

A reduction of 20% in the price of wheat a person enables to purchase 4 kg more for Rs. 160. Find the original price of wheat?

Direction: Study the pie chart carefully and answer the given questions. The pie chart shows the percentage breakup of students in different classes from VI to X in the year 2017

If in class VI, the ratio of boys to girls is 6:5 and the total number of girls in class VI is 50 less than that of the total number of girls in class VII. Find the ratio of the total number of boys in class VI to class VII.

If a-b=10 and ab=-21, then what is the value of a³-b³?

The height of a cone is 16 cm and radius of its base is 30 cm. If the rate of painting it is Rs.14/cm², then what will be the total cost in painting the curved surface of cone from outside?

Two guns were fired from the same place at an interval of 13 minutes but a person in a train approaching the place hears the second shot 12 minutes 30 seconds after the first. Find the speed of train if sound travels at 330 metres per second.