Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

Five lovely ladies(Sophia, Isabella, Madison, Emma and Olivia) planned a picnic.

They each buy one thing each for the picnic.

Sophia, Emma and Olivia got a drink : orange-Juice, apple-juice, and mango-juice.
Olivia got the drink with the same letter as the one in her first name.
Emma loves mango-juice.
The other two bring some food : chocolates and pizza.
Also Madison is allergic to cheese.

So which ladies bought what ?

By removing one matchstick and adding one matchstick, can you convert the word "ZOO" to an animal name?

Prove that the below maths equation is true.

8 + 8 = 91

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see? What is it?

You are given a cube that is made with the help of 10x10x10 smaller cubes summing up to a total of 1000 smaller cubes. You are asked to take off one layer of the cubes.
How many remain now?

What is the below Rebus indicate?

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

Why is 6 afraid of 7?