Virginia SOL 2.CE.1.a
The Standard
Apply strategies (e.g., rounding to the nearest 10, compatible numbers, other number relationships) to estimate a solution for single-step addition or subtraction problems, including those in context, where addends and minuends do not exceed 100.
Virginia Standards of Learning for Mathematics · The student will recall with automaticity addition and subtraction facts within 20 and estimate, represent, solve, and justify solutions to single-step and multistep problems, including those in context, using addition and subtraction with whole numbers where addends or minuends do not exceed 100.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students replace numbers with nearby tens or compatible numbers, then use mental addition or subtraction to find an approximate answer. They choose a strategy that fits the numbers and explain why the estimate is reasonable in a word problem.
What Mastery Looks Like
- A student shows adjusted numbers, such as changing 47 + 32 to 50 + 30 and estimating 80. For subtraction, the student keeps the numbers in order, names the strategy, and checks that the estimate fits the situation.
Common Misconceptions
- Students may give an exact answer when asked to estimate, or think only one estimate can be correct. They may round 45 down, reverse numbers in subtraction, or choose friendly numbers too far from the original values.
How to Assess It
- Use this exit ticket: “A class has 58 pencils and gives away 27. About how many remain? Show your estimation strategy and explain your answer.”
Lesson moves
Ways to Teach It
Give pairs of two-digit number cards; students place each on an open number line, round to tens, and estimate the sum or difference.
Ask, “For 34 + 48, is 70 or 80 a better estimate?” Students write two sentences defending their choice.
Play Estimate Match: students pair problem cards with estimate cards, then earn a point by naming the strategy used.
Use a pretend $100 class budget; students estimate the money left after one purchase or the total cost of two items.
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Printable 2.CE.1.a Worksheet
A ready-to-print activity worksheet aligned to 2.CE.1.a, with an answer key for the teacher on its own page. No account needed.
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