Find the next number in the series below

21 32 54 87 131 ?

A bridge is about to collapse. There are four people P, Q, R and S on one of the sides. Before the bridge collapses, they want to cross it. Now since the bridge is too weak, it can only stand the weight of two people at a time. Also, it is night time and nothing is visible. They have just one torch with them.

Now P takes one minute to cross the bridge, Q takes two minutes to cross, R takes five minutes to cross and S takes ten minutes to cross.

The bridge will collapse in seventeen minutes. How will they be able to cross the bridge before it collapses?

Can you find the odd number in the following?

2716, 4135, 5321 and 7145

Can you find the missing number in the third row?
35 20 14
27 12 18
5 2 ?

Complete the table series riddle by finding the number that can replace "??".

A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?

What is the next number in this series?

4,12,84,3612....

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

What is the centre of gravity?

Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?