Can you fill the blank with the correct number?

6 30 870 756030 _____

What does below rebus means ?

John can place six large boxes or nine small boxes into a carton.

Can you find out in how many cartons can he place sixty-six boxes in total?

If a shopkeeper can only place the weights on one side of the common balance. For example, if he has weights 1 and 3 then he can measure 1, 3 and 4 only. Now the question is how many minimum weights and names of the weights you will need to measure all weights from 1 to 1000? This is a fairly simple problem and very easy to prove also.

What Does this text mean:

important=important

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

Speaking of rivers, a man calls his dog from the opposite side of the river. The dog crosses the river without getting wet, and without using a bridge or boat. How?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

Who is that with a neck and no head, two arms and no hands? What is it?