Addition and subtraction to 10,000

Subtract from the right. If a place does not have enough units, borrow from the left. Use the reduced digit in the next step and borrow again if needed.

Add the subtracted number to the difference to find the starting number. Check by carrying out the subtraction.

Do not skip zeros. If you cannot borrow from the next column, move left to a nonzero digit. Record the changed digits before continuing the subtraction.

Start with the ones. If their sum is at least 10, write the ones digit and carry 1 to the tens column. Include that carried ten.

Align equal place values. Zeros mark empty places: do not skip them. Add from the right and carry 1 when needed.

To borrow across zeros, find the nearest nonzero digit on the left and reduce it by 1. Intervening zeros become 9 and the place being borrowed into receives 10 units.

If there are not enough ones, exchange 1 ten for 10 ones. After subtracting the ones, use the tens digit reduced by 1.

Align ones, tens, hundreds and thousands. Trailing zeros do not change the other addend in those places. Still check whether any carry is needed.

Subtract the difference shown after the equals sign from the first number. The result is the missing subtrahend. Check it in the original calculation.

Check both operations: addition and subtraction. Choose the sign that gives the number on the right.

Add ones to ones, tens to tens, hundreds to hundreds and thousands to thousands. No column needs a carry.

Subtract the known addend from the sum. Put the result in place of the question mark and check the addition.

Add from the right. If a column total is exactly 10, write 0 there and carry 1 to the left. Remember the final carry.

Subtract ones from ones, tens from tens, hundreds from hundreds and thousands from thousands. Start at the rightmost column.

Align equal place values and subtract from the right. Check by adding the subtracted number to your difference: you should recover the starting number.

Add from right to left. Include any 1 carried from the previous column. If a column total is at least 10, carry 1 to the next column.