How many bricks does it take to complete a building that is 15 feet wide, 30 feet deep, and 12 feet tall made of brick?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

John drives to his office at 20km/hr. After reaching the office, he realizes that today is a holiday. He went back at an average speed of 30km/hr. Discounting the time spent in the stoppage what was the average speed of his journey?

Count the number of squares in the picture below.

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

What does this rebus mean?

O
N
C
E
TIME

How can one talk without saying a single word?

If you drop a 15 kg iron bar and a 5 kg bag of cotton from a height of 50 meters which will reach the ground first?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?