How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?

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 5-letter word typed in all capital letters can be read the same upside down?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Find the next number in the series

12, 20, 40, 72, 116, 172 ?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?

The doctor advised his patient to take a tablet after every fifteen minutes. He gave him five tablets in total.

How much time will he take to have all the five tablets?

In a particular village, only two barbershops exist.

The first shop has a handsome barber with a neat haircut who is handsomely dressed in clean clothes and is extremely humble with his body language. The place is clean and looks hygienic.

In the second shop, you can find a barber with shabby clothing. His hairs are weirdly cut and his clothes still have the stains from last night's dinner. The place is not clean as well and reeks a bit.

You visit the village for the first time and decide to get your haircut. Which barbershop will you like to go for that and why?

What number comes next in this sequence:
7 8 5 5 3 4 4 _