900 is 1/10 of what.

For this answer, you have to divide, so the problem will be 900 divided by 1/10. Since it's division, you flip the fraction behind the division sign and change the division to multiplication. This is called K (keep) F (flip) C (change) cause you keep the first number, flip the second number (only if it is a fraction) and change the division sign.

Now the problem should be:

900 times 10/1 or 900 times 10 which equals to 9000!