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Subtract multiples of 10 mentally

Subtracting a multiple of 10 means removing a specified number of tens, so the ones digit remains unchanged while the tens and, when necessary, hundreds are adjusted according to place value. This includes mentally subtracting nonnegative multiples of 10 from two- and three-digit numbers within 1,000, including regrouping a hundred as ten tens when needed; larger numbers and more general written subtraction algorithms are outside this scope.

Detailed Explanation: Subtract multiples of 10 mentally

To subtract a multiple of (10)(10), think about tens. The ones digit stays the same because you are not subtracting any ones.

Example:

326−80326-80
  1. (80)(80) is 88 tens.
  2. The number (326)(326) has 22 tens, but we need to take away 88 tens. Regroup 11 hundred as (10)(10) tens:
326=2 hundreds +12 tens+6 ones. 326=2\text{ hundreds }+12\text{ tens}+6\text{ ones}.
  1. Subtract 88 tens from (12)(12) tens:
12−8=4 tens. 12-8=4\text{ tens}.
  1. Keep the 66 ones unchanged.

So,

326−80=246326-80=246

You can check: (246+80=326)(246+80=326).

Learn by doing: Subtract multiples of 10 mentally

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    Subtraction - Whole Number - Subtract Multiple of 10 from a Number - Columns

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