If it took eight men ten hours to build a wall, how long would it take four men to build it?

What is the relationship between these matchstick pictures below?

There are five people. One of them shot and killed one of the other five.
We know following clues:
1. Dan ran in the NY City Marathon yesterday with one of the innocent men.
2. Mike consider being a farmer before he moved to the city.
3. Jeff is a top notch computer consultant and wants to install Ben new computer next week.
4. The murderer had his leg amputated last month.
5. Ben met Jack for the first time six months ago.
6. Jack has been in seclusion since the crime.
7. Dan used to drink heavily.
8. Ben and Jeff built their last computers together.
9. The murderer is Jack's brother. They grew up together in Seattle.

Consider yourself to be a famous detective "Sherlock Homles", Can you find the killer?

If Rajina's daughter is my daughter's mom, who am I to Rajina?

Move three sticks of the spiral below to form a square.

What is the centre of gravity?

What question can you never answer yes to?

Replace the question mark with the correct number.

Can you find the hidden animal in the picture below?

If,

A + B = C
D - C = A
E - B = C

Based on the above equations, find out the answer for:

D + F = ?