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

In a contest, four fruits (an apple, a banana, an orange, and a pear) have been placed in four closed boxes (one fruit per box). People may guess which fruit is in which box. 123 people participate in the contest. When the boxes are opened, it turns out that 43 people have guessed none of the fruits correctly, 39 people have guessed one fruit correctly, and 31 people have guessed two fruits correctly.
How many people have guessed three fruits correctly, and how many people have guessed four fruits correctly

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

All of the flowers I have are orchids except two. All of the flowers I have are hibiscuses except two. All of the flowers I have are roses except two.

Can you tell me how many flowers I have?

What four weights can be used to balance from 1 to 30 pounds?

Identify the hidden meaning behind this picture?

A man died, leaving $10,000,000 for his widow, 5 sons and 4 daughters. Each daughter received an equal amount, each son received twice as much as a daughter, and the widow received three times as much as a son.

How much did the widow receive?

Can you move 2 matchsticks to form four equal sized squares.

What does the below image rebus riddle means ?

Why is it very easy to weigh a fish?