Times Table Answers

9 x 100 = 900

9 times 100 is 900. Shift the 9 two columns left, or take the easier route and subtract 100 from 1000. Both land on nine hundred, and 900 has a few properties worth knowing.

9 × 100 = 900

Adding 9 to itself 100 times gives the same answer.

Two ways to get there

Multiplying by 100 moves the 9 two columns to the left, from units to hundreds, with two zeros filling in behind it: 900.

If shifting digits feels fiddly, go the other way. Ten hundreds is 1000, so nine hundreds is one hundred less: 1000 – 100 = 900. Every multiple of 9 can be reached like this, by taking one lot away from the round ten above it.

900 is a square number

9 is 3 x 3 and 100 is 10 x 10, so their product is a square as well, with root 3 x 10 = 30. That gives 30 x 30 = 900. There is a second signature too: the digits of any multiple of 9 add up to a multiple of 9, and here 9 + 0 + 0 = 9.

900 as a quantity

900 seconds is exactly 15 minutes, a quarter of an hour, because 15 x 60 = 900. And 900 degrees is two and a half full turns — 360 + 360 + 180 — which is where the skateboarding trick called a 900 gets its name. Both are handy sanity checks: if a figure of 900 seconds or 900 degrees does not come out as a clean quarter hour or two and a half spins, the arithmetic went wrong somewhere earlier.

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