Quantitative Aptitude - Arithmetic Ability Questions

In a class there were 28 boys and some girls. In a test the mean score obtained by the boys was 12.5 while that obtained by the girls was 14.5. If the overall average was 13.1, what was the total number of students in the class?

The average revenues of 11 consecutive years of a company is Rs 69 lakhs. If the average of first 6 years is Rs 64 lakhs and that of last 6 years is Rs 76 lakhs, what is the revenue for the 6th year?

A batsman makes a score of 81 runs in the 16th match and thus increases his average runs per match by 3. What is his average after the 16th match?

A miner sells a diamond to a trader at a profit of 40% and the trader sells it to a customer at a profit of 25%. If the customer pays Rs 56 lakhs to buy the diamond, what had it cost the miner (in Rs lakhs)?

3/5 of my current age is the same as 5/6 of that of one of my cousin. My age ten ago will be his age four years hence. My current age is ___ years.

ax + 5y = 8 has slope of -4/3. What is the value of a?

If Cos θ = 15/17 , then what is the value of Cosec θ?

If by increasing the price of a ticket in the ratio 8:11 the number of tickets sold fall in the ratio 23:21 then what is the increase (in Rs) in revenue if revenue before increase in price of ticket was Rs 36,800?