A bank offers 10% compound interest per half year. A customer deposits Rs. 3600 each on 1st January and 1st July of a year. At the end of the year, the amount he would have gained by way of interest is.
In a college, the ratio of boys to girls is 29 : 33 respectively. When 142 more boys join the college, this ratio becomes 21 :19. How many more girls should join the college to make the number of boys and girls equal?