A goldsmith observes that one of his employees prepares a necklace in 9 hours, while another employee prepares it in 10 hours. If they work together, they stud 10 gems less every hour and thus prepare a necklace in 5 hours, then the number of gems studded in each necklace is: 

What will come in place of the question mark (?) in each of the following series?

15     18    16   19     17    20    ?

The ratio of income & savings of a man is in ratio of 16:3 respectively. If his savings increases by 1/3 rd and expenditure increased by 1/2, then find the ratio of new income to earlier income of man?

A clock runs fast by 5 mins per hour. If the clock was set right at 12 noon and the clock shows 6.30 p.m. now, what is the right time? 

The average of nine numbers in M and the average of three of these is P. If the average of remaining numbers is N, then