What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

You are confined in a room and given two metal rods. Out of these two rods, one is magnet and the other is the iron rod. They look starkly similar. You don't have any other metal object in the room.

How will you decide which one of those is magnet?

Manish has to secure 40% marks to pass his B.tech final exams.
He got just 40 marks and failed by 40-marks.

What is the maximum marks?

Can you solve the tricky chess rebus puzzle below by ciphering the hidden meaning?

I have four wings but can't fly.
I express no emotions.
I am found on the exact spot every time you look.
I keep toiling away with a little sound.

Do you know what am I?

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

Move four matchsticks to the below square to form three squares?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Why is a river so rich ?

I have a big mouth and I am also quite loud! I am NOT a gossip but I do get involved with everyone's dirty business.