Why does 10 x 9 = 90?

Because adding 10 9's together makes 90.

That is, because 91 + 92 + 93 + 94 + 95 + 96 + 97 + 98 + 99 + 910 = 90.

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Why does 10 x 9 = 90?

Because adding 10 9's together makes 90.

That is, because 91 + 92 + 93 + 94 + 95 + 96 + 97 + 98 + 99 + 910 = 90.

Keep practicing