Quantitative Aptitude - Arithmetic Ability Questions

A boy multiplied 987 by a certain number and obtained 559981 as his answer. If in the answer both 98 are wrong and the other digits are correct, then the correct answer would be ?? please explain in detail

Pipe A is an inlet pipe that can fill an empty cistern in 69 hours. Pipe B can drain the filled cistern in 46hours. When the cistern was filled the two pipes are opened one at a time for an hour each, starting withPipe B. how long will it take for the cistern to be empty?

Two typists of varying skills can do a typing jobin6 minutesifthey work together.Ifthe first typist typed alone for 4 minutes and then the second typist typed alone for 6 minutes, they would be left with 1/5 of the whole work.Howmany minutes would it take the slower typist to complete the typing job working alone?

A man buys a watch for Rs1950 in cash and sells it for Rs 2200 at a credit of 1 yr. The rate of interest is 10% per annum. Then he gains or loose how much amount?

A sum becomes Rs 2286 in 3 years and Rs 2448 in 4 years at simple interest. What is the rate (in percentage) of interest per annum?

21% of 500 + 31% of 1100 - 30% of 790 = ? 

5% of a = b, then b% of 20 is the same as __________.

Cost of 8 pencils, 5 pens and 3 erasers is Rs 111. Cost of 9 pencils, 6 pens and 5 erasers is Rs 130. Cost of 16 pencils, 11 pens and 3 erasers is Rs 221. What is the cost (in Rs) of 39 pencils, 26 pens and 13 erasers?