What always comes into a house through the keyhole?

You along with your friend are standing in front of two houses. Each of those houses inhabits a family with two children.

Your friend tells you the below two facts:
1) On your left is a family that has a boy who likes accounts but the other child loves science.
2) On the right is a family with a seven-year-old boy and a newborn baby.

You ask him, "Does either of the family have a girl?"

To this, he replies, "I am not quite sure. But can you guess that? If you are right, I will give you $500."

Which family do you think is likely to have a girl?

Which three-digit number, made of consecutive digits, like 567, is 2 less than a cube and 2 more than a square?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

Prove that the below maths equation is true.

8 + 8 = 91

Replace the question mark with the correct number below.

It is a nine-letter word.
The exact opposite of the phrase "friendly and outgoing"
It contains the word "over".
It starts will a vowel.

What is it?

Forwards I am heavy, backward I am not. What am I?

I went to the bookshop and spent one-half of the money that was in my purse.

When I came out, I found that I had as many cents as I had dollars and half as many dollars as I had cents when I went in. Find the money in my purse when I entered the store.

Which city is three-fifths chick two third cat and 50% goat?