Multiply Before Adding
Part of the Numbers & Operations section of Coddy's Pre-Algebra journey. Lesson 7 of 60.
What is 2 + 3 × 4? Working left to right gives 5, then 20. But the agreed answer is 14: multiplication comes before addition. First 3 × 4 is 12, then 2 + 12 is 14.
Why this order? A product like 3 × 4 is one quantity, three fours bundled together, so it is worked out before it joins a sum. The rule is also an agreement: without it, the same line could mean two different numbers, and nobody could check anybody else's work.
On the board, the multiplication goes first in your next line. Type 20 after 2 + 3 × 4 and the board refuses it, because 20 is not the value of that line.
Challenge
Work out 7 + 6 × 5.
Try it yourself
Simplify the expression
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Numbers & Operations
1Working on the Board
Your First AnswerType the Next LineOne Line at a TimeDots and BarsFriendly ProductsRecap: Board Work4Adding Integers
Adding Two NegativesDifferent SignsZero PairsAdding Several IntegersRecap: Adding Integers2Order of Operations
Multiply Before AddingLeft to RightParentheses FirstBrackets Inside BracketsThe Fraction Bar GroupsRecap: Order of Operations5Subtracting Integers
Add the OppositeSubtracting a NegativePlus and Minus in a RowDistance Between NumbersRecap: Subtracting Integers