I am white when I am dirty, and black when I am clean. What am I?

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?

You order chicken wings at KFC in the boxes of 6, 9 and 20. What is the largest number of wings that you cannot obtain by buying in any combination of the boxes?

Which of the following words don't belong in the group and why?
CORSET, COSTER, SECTOR, ESCORT, COURTS

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

I am an eight letter word and I am a computer terminology.
The second, third and fourth letters make an animal.
The fourth, fifth, sixth, seventh and eighth letters make a weapon.
The first, second, third and fourth letters can be taken as an outcome of any exam.
The fifth, sixth, seventh and eighth letter combine to form a high end typing software.

Can you tell who am I ?

In the given picture, you can find a square in the centre and four open squares. Can you form three closed squares by just moving three sticks from their positions respectively?

I am green and found in the forest and have needles instead of leaves. What am I?
Hint 1: It can be used for Christmas decorations.
Hint 2: I have a strong, scent that is used in air fresheners.

What can go up a chimney down, but can't go down a chimney up?

On a certain day, John celebrated his birthday. Two days later, his older twin brother Jacob celebrated his birthday.

Is this even possible? How can it be?