Virginia SOL 1.CE.1.g
The Standard
Determine the unknown whole number that will result in a sum or difference of 10 or 20 (e.g., 14 - __ = 10 or 15 + __ = 20).
Virginia Standards of Learning for Mathematics · The student will recall with automaticity addition and subtraction facts within 10 and represent, solve, and justify solutions to single-step problems, including those in context, using addition and subtraction with whole numbers within 20.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students find the missing number in an addition or subtraction equation that ends at 10 or 20. They use known facts, counters, or counting to explain their answer.
What Mastery Looks Like
- A student quickly solves equations such as 13 + □ = 20 and 18 − □ = 10. The student checks each answer by putting it back into the equation.
Common Misconceptions
- Some students write the target number in the blank instead of finding the missing part. Others count in the wrong direction or move 10 spaces rather than stop at 10 or 20.
How to Assess It
- On an exit ticket, have students solve 17 − □ = 10 and 13 + □ = 20, then draw counters to check one answer.
Lesson moves
Ways to Teach It
Give pairs ten-frames and 20 counters; students build 16, then add or remove counters to make 20 or 10.
Ask, “How are 16 + □ = 20 and 16 − □ = 10 alike and different?” Students draw and explain.
Play Missing Number Match with equation cards and answer cards; partners pair them, solve aloud, and check with a number path.
Set up a shelf with 20 spaces and 13 cans; students find how many more cans are needed to fill it.
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Printable 1.CE.1.g Worksheet
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