Two trains of length 120 m and 90 m respectively with the same speed pass a static pole in 8 seconds and 6 seconds respectively. In what time they will cross each other if they are moving in opposite directions?

The area of trapezium is 21 square cm, the distance between the parallel sides is 3 cm and one of the parallel sides is 8.3 cm. What is the length of the other parallel side ?

In an election there were two candidates, one candidate got 30% of the votes and lost by 16000 votes, how many votes were cast in total?

The Population of vultures in a particular locality is decreases by a certain rate of interest (compounded annually). If the current population of vultures be 29160 and the ratio of decrease in population for second year and third year be 10: 9. What was the population of vultures 3 years ago? 

A and B started a business with investments Rs 3500 and Rs 2500 respectively. After 4 months C joined with Rs 6000. If the difference between C's share and B's share in the annual profit was Rs 1977, what was the total annual profit? 

Ravi purchases 90 pens and sells 40 pens at a gain of 10% and 50 pens at a gain of 20%. Had he sold all of them at a uniform profit of 15% he would have got Rs. 40 less. Find the cost price of each pen.

Direction (66-70): What should come in place of the question mark(?) in the following number series?

4, 5, 14, 51, ?