What is black when you buy it, red when you use it, and gray when you throw it away?

When can we add 2 to 11 and get 1 as the correct answer?

Can you solve the tricky chess rebus puzzle below by ciphering the hidden meaning?

If 2 workers can complete painting 2 walls in exactly 2 hours.

How many workers would be needed to paint 18 walls in 6 hours?

I shave every day, but my beard stays the same. What am I?

Can you find the least possible number such that

If the number is divided by 3, it gives the remainder of 1;
If the number is divided by 4, it gives the remainder of 2;
If the number is divided by 5, it gives the remainder of 3;
If the number is divided by 6, it gives the remainder of 4.

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

John can fit six large chocolate boxes or nine small chocolate boxes into a carton. How many cartons will he require to put sixty-six chocolate boxes into?

A Shopkeeper collects 71 rupees in the form of 20 paisa and 25 paisa.
He collects a total of 324 coins.

Can you tell me how many number of 20-paisa and 25-paisa he got?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?