Can you replace the question mark with the correct number?

In the image given, you can find several triangles. Can you count them all?

There are 2 sand hourglasses.

The small one can measure 5 hours and the large one can measure 7 hours.

How can we measure 16 hours with 2 sand hourglasses running together ?

You have two buckets - one holds exactly 5 gallons and the other 3 gallons. How can you measure 4 gallons of water into the 5 gallon bucket?

(Assume you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.)

I have branches, but no fruit, trunk or leaves. What am I?

What is the value of 1/2 of 2/3 of 3/4 of 4/5 of 5/6 of 6/7 of 7/8 of 8/9 of 9/10 of 1000?

Which five letter word can be added at the end of below word to form a
valid word?

> Pin
> Check
> Boiling
> View

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

John was working on a Chemical Mixture whose weight comprise 90% liquid and 10% solid. The total weight of the mixture is 20 pounds. After a while, John noticed that some of the liquid evaporated and now the liquid comprises just 50% of the weight.

What is the weight of the chemical mixture now?