How many words can a pen with half refill write?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

I can write cow in 13 letters.

Can You?

I cry without having a voice.
I fly without having wings.
I bite without having teeth.
I whisper without a mouth.

Who am I?

Can you solve this tricky maths equation problem by replacing it? mark with the correct symbol?

19834 -----: 187
15921 -----: 153
17561 -----: 139
13734 -----: ???

What is the next number in this series?

4,12,84,3612....

Outside a tattoo artist's shop, there was a signboard which read 'I make tattoos on only them who do not tattoo themselves'.

Reading it what do you think, does the tattoo artist tattoo himself?

Find the Goldfish below the given Image.

1 dollar = 100 cent
= 10 cent x 10 cent
= 1/10 dollar x 1/10 dollar
= 1/100 dollar
= 1 cent

=> 1 dollar = 1 cent

solve this tricky problem?