I am white when I am dirty, and black when I am clean. What am I?

Can you find the missing piece of the Porsche?

Why do we preferably have round manhole covers and not square ones?

John walks into the daily grocery shop and steals a $100 bill from the shop. An hour later John returns to the shop and buys some daily products for $40. John pays the owner the $100 bill and therefore the owner returns him $60.

How much money did the owner lose?

I cannot talk, but I always reply when spoken to. What am I?

Jenifer and Jesica are having a conversation.

Jenifer: I am definitely not over 30.
Jesica: I am 28 and you are surely 5 years older to me at least.
Jenifer: No, you are at least 29.

You are told that both of them are lying throughout in the conversation. Can you find their respective ages?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

Which Number is the odd one out?

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

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?

If,

6 / 7 = 2
3 / 9 = 7
8 / 2 = 6

Then

4 / 5 = ?