Lessons for 3.OA.D.8
Using a letter for the unknown numberA letter stands for the number we do not know yet in an equation that models a story.Lesson
Mental strategiesMake a ten, double and halve, break apart: computing without paper.Lesson
Problems using several operationsStories that need two or more of the four operations in a chosen order.Lesson
Estimating by roundingRound first, then compute, to check a result makes sense.Lesson
Two-step addition and subtraction problemsStories that need one answer worked out before the next.Lesson
Printable Worksheets
Using a letter for the unknown number worksheet (PDF)Printable worksheet with answer keyPreview
Problems using several operations worksheet (PDF)Printable worksheet with answer keyPreview
Estimating by rounding worksheet (PDF)Printable worksheet with answer keyPreview
Two-step addition and subtraction problems worksheet (PDF)Printable worksheet with answer keyPreview