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Subtract from a two-digit number without regrouping informally

The learner understands subtraction within 100 as finding the difference between a two-digit quantity and a smaller quantity when each place can be subtracted without exchanging a ten: tens are removed from tens and ones from ones. They can reason with place-value drawings, decomposed numbers, or jumps on a number line, recognizing that the digits represent quantities rather than independent symbols; regrouping, larger numbers, and the standard subtraction algorithm are beyond this understanding.

Detailed Explanation: Subtract from a two-digit number without regrouping informally

To subtract, take away the tens first and then take away the ones.

Example:

47−2347-23

Think of 4747 as 4 tens and 7 ones. Think of 2323 as 2 tens and 3 ones.

  1. Take away 22 tens from 44 tens:
4 tens−2 tens=2 tens4\text{ tens}-2\text{ tens}=2\text{ tens}
  1. Take away 33 ones from 77 ones:
7 ones−3 ones=4 ones7\text{ ones}-3\text{ ones}=4\text{ ones}
  1. Put the tens and ones left together:
2 tens+4 ones=242\text{ tens}+4\text{ ones}=24

So,

47−23=2447-23=24

Learn by doing: Subtract from a two-digit number without regrouping informally

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    Base 10 Blocks - Subtracting - Picture to Answer, No Borrow - Tens and Ones

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