2 ladies and 2 girls need to cross a river in a boat big enough for 1 LADY or 2 girls. How do they do it?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

What occurs twice in a week, once in a year but never in a day?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

There are nine letters in the below-given diagram. You have to form a nine-letter word using these letters.

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

What has 13 hearts but no other organs?

Before reading ahead, you must know the fact that only one of the people here is telling the truth.

A says that B is lying.
B says that C is lying.
C says both A and B are lying.

Can you find out who is speaking the truth?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.