Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not-rounded numerals equals 24.

What can you catch but never throw?

What has 13 hearts but no other organs?

Find three whole, positive numbers that have the same answer when multiplied together as when added together.

Can you replace the question mark with the correct number?

If a boy blows 18 bubbles,
Then pops 6 eats 7 and then
He pops 5 and blows 1.
How many are left?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

What is full of holes but still holds water?

I add 5 to 9 and get 2. The answer is correct, so what am I?

Replace the question mark with the correct number below.