Take Away the Total
Part of the Numbers & Operations section of Coddy's Pre-Algebra journey. Lesson 8 of 57.
Changing the order works for adding and multiplying. It does not work for taking away. But there is another shortcut: add up what you take away.
12 - 5 - 3 takes away 5, then 3. That is 8 in total. So it is the same as 12 - 8, which is 4.
A common slip is to work out 5 - 3 first. That gives 12 - 2, which is 10. That is wrong.
With round numbers it is fast. In 90 - 18 - 32, 18 and 32 make 50. So it is 90 - 50, which is 40.
Challenge
You have 200 dollars. You pay three bills: 46, 54 and 35 dollars. That is 200 - 46 - 54 - 35. How much is left?
Try it yourself
200 - 46 - 54 - 35
Simplify the expression
All lessons in Numbers & Operations
1Order of Operations
Your First AnswerLeft to RightParentheses FirstBrackets Inside BracketsThe Fraction Bar GroupsRecap: Order of Operations4Adding Integers
Adding Two NegativesDifferent SignsZero PairsAdding Several IntegersRecap: Adding Integers5Subtracting Integers
Add the OppositeSubtracting a NegativePlus and Minus in a RowDistance Between NumbersRecap: Subtracting Integers