Quantitative Aptitude - Arithmetic Ability Questions

A boy found the answer for the question "Subtract the sum of 1/4 and 1/5 from unity and express the answer in decimals" as 0.45. The percentage of error in his answer was

The incomes of X and Y are in the ratio 5 : 6 and their expenditure are in the ratio 6 : 5. If X saves Rs 7000 and Y saves Rs 15000, then what will be the income (in Rs) of X?

Tom's father is thrice as old as Tom. 10 years ago Tom's father's age was 7 times his age. What is Tom's current age? 

The average temperature of Monday ,Tuesday , Wednesday and Thursday is 60°, The average for Tuesday, Wednesday, Thursday and Friday is 63°; If the ratio of temperature for Monday and Friday is 21 : 25, then what is the temperature of Friday ?

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 shopkeeper marks up his wares by 80% and offers 20% discount. What will be the selling price (in Rs) if the cost price is Rs 450?

Selling price of a watch is Rs 966 and profit percentage is 15%. If selling price is Rs 798, then what will be the loss percentage?

Mr. Mike borrowed Rs. 8500 at 4% per annum C.I. The C.I. compounded annally for 2 years is :