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

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

Which Burger Is Different in below image?

Which is heavier: a ton of bricks or a ton of feathers?

Replace the question mark with the correct number in below Picture:

I have two sand hourglasses:
1. A 7 minute one and
2. An 11-minute one.

Using just these 2 sand hourglasses, how can I measure time as 15 minutes?

The teacher told the student that if he told a lie then he will be expelled from school and if he told the truth then he still is expelled from school.

What can a student say to prevent his being expelled from school?

Find the 8 in the below-given Image.

What does this rebus mean?

O
N
C
E
TIME

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.