Before Mount Everest was discovered, what was the highest mountain in the world?

Solve this riddle by finding the odd one out from the rest.

Use the digits from 1 up to 9 and make 100.

Follow the rules.
=> Each digit should be used only once.
=> You can only use addition.
=> For making a number, two single digits can be combined (for example, 4 and 2 can be combined to form 42 or 24)
=> A fraction can also be made by combining the two single digits (for example, 4 and 2 can be combined to form 4/2 or 2/4)

Question: how can we do this?

How is a fly different from a mosquito?

The following alphametic has only one solution. Can you find it?
ENLIST + SILENT + LISTEN = ANAGRAM

PS: You may start the number from 0.

Find the number of squares in the below-given picture.

What has no start, end, or centre?

What goes up but never comes down?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?