Subtracting More Than Two ValuesWhen you are working with more than two values in a long problem, you need to keep all of the values in place. We said it was important that you keep values in order when you are subtracting. You can't regroup numbers and you can't reorder numbers. You will get an answer if you do, but it will be the wrong answer. When you have more than two values in a subtraction problem, order is everything.
You know that 6 - 3 is not the same as 3 - 6.
6 - 3 = 3
3 - 6 = -3 (when you work with integers)
What if you get the problem 9 - 3 - 4?
You really have to keep the numbers in the correct order and move from left to right when you subtract. If your problem is in a vertical format, start with the top two values and then move down. In both directions, you will work with two numbers at a time. Once you get the first difference, you use that for the next step. So for our example...
9 - 3 - 4 = ?
(1) First part: 9 - 3 = 6
(2) Use the 6 in the next part: 6 - 4 = 2
Answer: 9 - 3 - 4 = 2
On a Number LineSo let's look at an example on a number line. It might help you to see how this is all working. Start with the first two values on the left and then do one more at a time.
18 - 6 - 5 - 4 = ?
And now what does this look like on a number line?
[number line image of problem]
So you get the answer 3. Can you see how you make three jumps? Step by step you get to the final answer.
Do It in a SeriesBut what if you have five values? We admit that would be one hard subtraction problem, but it can be done. Just keep all of the numbers in order. Small steps will give you the correct answer.
89 - 20 - 16 - 11 - 21 = ?
- or -
Steps to Solve:
Step 1: 89 - 20 = 69 (Top two values)
Step 2: 69 - 16 = 53 (First difference and third value)
Step 3: 53 - 11 = 42 (Second difference and fourth value)
Step 4: 42 - 21 = 21 (Third difference and fifth value)
89 - 20 - 16 - 11 - 21 = 21
Grouping ValuesOne last reminder before we go. You learned about grouping values in addition. Can you do the same thing with subtraction? No. You will learn some grouping shortcuts in the future, but there are no simple ways. Just go step-by-step for now.
- 1 to 10
- 1 to 20
- 2-Digit Numbers
- 3-Digit Numbers
- Multiple Values
Useful Reference MaterialsWikipedia: