Year 4 Math: Unit 3. Multiply a 3-digit number by a 1-digit number- Study Notes , Worksheets and Online Tests

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To multiply a 3-digit number by a 1-digit number using the standard algorithm, you would follow these steps:

  1. Write the 3-digit number and the 1-digit number side by side.
  2. Multiply the ones digit of the 3-digit number by the 1-digit number. Write this product below the line, in the ones place.
  3. Multiply the tens digit of the 3-digit number by the 1-digit number. Write this product below the line, in the tens place.
  4. Multiply the hundreds digit of the 3-digit number by the 1-digit number. Write this product below the line, in the hundreds place.
  5. Add the three products from step 2, 3, and 4.

For example, let’s say you want to multiply 345 by 7:

345
x 7
—–
 
  • Multiply the ones digit (5) by the 1-digit number (7) to get 35.
  • Multiply the tens digit (4) by the 1-digit number (7) to get 28. multiply 10 = 280
  • Multiply the hundreds digit (3) by the 1-digit number (7) to get 21. Multiply 100 = 2100
  • add 2100, 280, 35 = 2415

So, 345 x 7 = 2415

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