If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

Count the number of triangles in the below picture?

Find the next number in the series below

21 32 54 87 131 ?

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

Count the number of triangles in the given picture.

Which Number is the odd one out?

A) 7145
B) 2716
C) 5321
D) 4135

What does this mathematical rebus means ?

It belongs to you, but other people use it more than you do. What is it?

There was a greenhouse.
Inside the greenhouse, there is a white house.
Inside the white house, there is a red house.
Inside the red house, there are lots of babies.

What is It?