Find out the missing number in the picture attached:

Which tank will fill first?

In four steps you need to move the word 'cold' From 'warm' by replacing one alphabet at a time such that every word formed at each step is acceptable in English Dictionary.

You have a basket containing ten apples. You have ten friends, who each desire an apple. You give each of your friends one apple.
Now all your friends have one apple each, yet there is an apple remaining in the basket.
How?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

Can you find out the total number of triangles in the given figure?

I am beautiful, up in the sky. I am magical, yet I cannot fly. To people I bring luck, and to some people, riches. The boy at my end does whatever he wishes. What am I?

What's a single-digit number with no value?

Using eight eights and addition only, can you make 1000?

Which three-digit number, made of consecutive digits, like 567, is 2 less than a cube and 2 more than a square?