0.8% of a number is 31, then find the number.

Ratio of CP and SP is 12:13, then the profit percent is?

Bananas are bought at 3 for Rs. 2 and sold at 5 for Rs. 4. Find the gain or loss percent.

Find the sum of 2x terms of the series ( 1² - 2² + 3² - 4² + ___ ) 

The real number to be added to 13851 to get a number that is divisible by 87 is :

The ratio of number of boys and girls in a school of 720 students is 7 : 5. How many more girls should be admitted to make the ratio 1 : 1 ?

In a mixture of 25 liters, the ratio of acid to water is 4 : 1. Another 3 liters of water is added to the mixture. The ratio of acid to water in the new mixture is: 

What is the average of all numbers between 100 and 200 which are divisible by 13?