Multiplying a 2-digit number by 39
Follow the Following Steps:
- Select a 2-digit number.
- Multiply by 4.
- Add one zero.
- Subtract the original number.
- The 2-digit number chosen to multiply by 39 is 21.
- Multiply by 4: 4 × 21 = 84.
- Add one zero: 840.
- Subtract the original number:
840 - 21 = 819. - So 21 × 39 = 819.
- The 2-digit number chosen to multiply by 39 is 71.
- Multiply by 4: 4 × 71 = 284.
- Add one zero: 2840.
- Subtract the original number:
2840 - 71 = 2800 - 31 = 2769. - So 71 × 39 = 2769.