Skill 2A: Adding a 3-digit number to a 4-digit number

A 4-digit number plus a 3-digit number

6,274 + 859

1. Estimate first: round each number. 6,300 + 900 = 7,200, so the answer should be close to 7,200.
2. Write the numbers one above the other so that the ones line up, then the tens, hundreds and thousands. Start on the right.

   	1	1	1
   	6	2	7	4
   +		8	5	9
   	7	1	3	3

3. Add each column from right to left:

   • ones: 4 + 9 = 13. Write 3 and carry 1 into the tens column.
   • tens: 7 + 5 + 1 = 13. Write 3 and carry 1 into the hundreds column.
   • hundreds: 2 + 8 + 1 = 11. Write 1 and carry 1 into the thousands column.
   • thousands: 6 + 0 + 1 = 7. Write 7.
4. The answer is 7,133. It is close to the estimate of 7,200, so it is sensible.

Answer: 7,133