Solve the Sequential Subtraction: 20 - 6 - 5

Q: Why do I subtract from left to right instead of adding the numbers being subtracted?

Order of operations requires us to work from left to right when operations have the same priority. While 20 - 6 - 5 happens to equal 20 - (6 + 5), this shortcut doesn't work for mixed operations like 20 - 6 + 5.

Q: How can I double-check my sequential subtraction?

Use addition to verify! Start with your final answer and add back each number you subtracted: 9 + 5 = 14, then 14 + 6 = 20. If you get back to the original number, you're correct!

Q: Is there a faster way to do this in my head?

Yes! You can think of it as "20 take away 6 leaves 14, then 14 take away 5 leaves 9." Or use the fact that $ 6 + 5 = 11 $, so $ 20 - 11 = 9 $.

Q: What happens if I have more than three numbers to subtract?

The same rule applies! Keep working from left to right, subtracting one number at a time. For example: 30 - 8 - 3 - 2 becomes 22 - 3 - 2, then 19 - 2 = 17.

Sequential Subtraction with Multiple Terms

$20 - 6 - 5 =$

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Understand the problem

$20 - 6 - 5 =$

Step-by-step solution

First, subtract the second number from the first:

$20 - 6 = 14$

Then, subtract the third number from the result:

$14 - 5 = 9$

So, $20 - 6 - 5 = 9$

Final Answer

$9$

Key Points to Remember

Essential concepts to master this topic

Order Rule: Subtract numbers from left to right in sequence
Technique: First calculate 20 - 6 = 14, then 14 - 5 = 9
Check: Count backwards: 9 + 5 = 14, then 14 + 6 = 20 ✓

Common Mistakes

Avoid these frequent errors

Subtracting all numbers from the first term at once
Don't calculate 20 - 6 - 5 as 20 - (6 + 5) = 20 - 11 = 9! While this gives the same answer here, it breaks the left-to-right rule and will cause errors in more complex expressions. Always work from left to right, one operation at a time.

Practice Quiz

Test your knowledge with interactive questions

$$ 8 - 2 + 6 = $$

FAQ

Everything you need to know about this question

Why do I subtract from left to right instead of adding the numbers being subtracted?

Order of operations requires us to work from left to right when operations have the same priority. While 20 - 6 - 5 happens to equal 20 - (6 + 5), this shortcut doesn't work for mixed operations like 20 - 6 + 5.

What if I accidentally subtract in the wrong order?

You'll get the wrong answer! For example, if you calculate 6 - 20 - 5 = -19 instead of 20 - 6 - 5 = 9. Always start with the first number and subtract each following number in sequence.

How can I double-check my sequential subtraction?

Use addition to verify! Start with your final answer and add back each number you subtracted: 9 + 5 = 14, then 14 + 6 = 20. If you get back to the original number, you're correct!

Is there a faster way to do this in my head?

Yes! You can think of it as "20 take away 6 leaves 14, then 14 take away 5 leaves 9." Or use the fact that $6 + 5 = 11$ , so $20 - 11 = 9$ .

What happens if I have more than three numbers to subtract?

The same rule applies! Keep working from left to right, subtracting one number at a time. For example: 30 - 8 - 3 - 2 becomes 22 - 3 - 2, then 19 - 2 = 17.

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