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Mathematics · Grade 1

Addition and Subtraction within Twenty

Learners build reliable strategies for facts within 20: making a ten to add (8 + 6 = 8 + 2 + 4), going back through ten to subtract (13 − 4 = 13 − 3 − 1), using doubles and near doubles, and using fact families so every addition fact also gives two subtraction facts. Facts within 10 are practised for accuracy, never against a clock.

  • 3 lessons
  • About 65 minutes
  • Facts within 20 check: 8 questions
  • Ways to answer: fill in the blanks, choose an answer, match pairs, type a number, place on a number line and put in order
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What learners will discover

  • Add within 20 by making a ten, for example 8 + 6 = 8 + 2 + 4 = 14.
  • Subtract within 20 by going back through ten, for example 13 − 4 = 13 − 3 − 1 = 9.
  • Use doubles, near doubles and fact families to find facts, and add and subtract within 10 accurately.

Lessons

  1. Make a ten to add 5 steps3 practiceabout 22 min
  2. Back through ten to subtract 5 steps3 practiceabout 22 min
  3. Doubles and fact families 7 steps4 practiceabout 21 min
  4. Facts within 20 check 8 questions at the end

Keep exploring

Games to practice with

  • Number-Line HopHelp the frog hop to the right number — from counting to negative fractions.
  • Paint by AnswersSolve each space, dip your brush and watch a picture come to life.
  • Number TrainAll aboard! Load exactly the right number of animals onto the train.

More 1st grade math

Guide for grown-ups