Why do we preferably have round manhole covers and not square ones?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

If you excel at these types of visual challenges, you may have superior observation skills, heightened perceptual abilities, and above-average IQs. Find the deer and prove how sharp your eyes are.

You can win me and lose me but never buy me
You can not eat me and never want to part with me
I can make you cry or bring you joy
I am not a machine and definitely not a toy
You keep me but i am not forever just yours
You might find me in a case or on a shelf next to a vase
I am hard and i am tall if you bump me i am sure to fall
I am made of different materials and am at many events
If your lucky and fight hard I might be yours
What am I ?

Count the squares in the matchstick puzzle below?

How many bricks does it take to complete a building that is 15 feet wide, 30 feet deep, and 12 feet tall made of brick?

A man dies of old age on his 25 birthday. How is this possible?

Which point will the car reach to go out?

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?