One Line at a Time
Part of the Numbers & Operations section of Coddy's Pre-Algebra journey. Lesson 3 of 60.
Longer problems are worked in several lines, one small step each. 13 + 8 + 7: you may add any two of the numbers first, because adding in a different order does not change a sum. 13 and 7 make a round 20, so the first line is 20 + 8.
The next line finishes the job: 20 + 8 is 28. The board checks every line on its own, so a slip in the middle is caught right where it happens, not three lines later.
Looking for pairs that make a round number, like 13 and 7, is how quick mental arithmetic works. Writing one step per line keeps every step small enough to get right.
Challenge
Work out 16 + 9 + 14 in two lines. First pair the two numbers that make a round total, then finish.
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