When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

Solve the following series:
AZ, GT, MN, __, YB

How much will a 38° angle measure when looked at under a microscope that magnifies ten times?

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

A man is shown a portrait painting. He looks closely, then tells, “Brothers and sisters have I none, but that man’s father is my father’s son!” Who is the man in the portrait?

Jack was having a candle light dinner with his girlfriend. Suddenly a cold gush of wind entered through the open window and three of the ten candles were extinguished. Assuming that none of the other candles were extinguished.

How many candles are they left with in the end ?

If,
9 * 8 * 7 = 65
8 * 7 * 6 = 50
7 * 6 * 5 = 37

Find
6 * 5 * 4 = ?

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

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?