Maryland Math 1.NOS.E.10.b
The Standard
- 1.NOS.E.10
- Add within 100 including adding a two-digit number and a one-digit number and adding a two-digit number and a multiple of 10. Understand that when adding two-digit numbers, tens are added to tens, ones are added to ones, and sometimes it is necessary to compose or decompose a ten.
Use counting strategies and strategies based on place value (e.g., partial sums, making tens, etc.) to add.
Maryland College and Career Ready Standards for Mathematics (2025) · USE PLACE VALUE UNDERSTANDING AND PROPERTIES TO ADD AND SUBTRACT.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students add by counting on or breaking numbers into tens and ones. When the ones add up to ten or more, they make a new ten.
What Mastery Looks Like
- For 27 + 15, a student combines 3 tens and 12 ones, then makes 42. They can also start at 27, jump 10 to 37, then count on 5 to reach 42.
Common Misconceptions
- Some students count both numbers from one instead of counting on. Others write 312 for 27 + 15 because they put 3 tens next to 12 ones without making a new ten.
How to Assess It
- Ask students to solve 28 + 14. Have them draw tens and ones or show counting-on jumps, then mark where they made a new ten.
Lesson moves
Ways to Teach It
Build 27 and 15 with connecting cubes, combine the loose cubes, and trade ten loose cubes for a stick of ten.
Write a counting-on path for 28 + 14, then tell a partner where you crossed a ten.
Play Add and Check: draw two cards labeled 10 to 39, add with number-line jumps, and check with tens sticks.
Draw 28 apples and 14 oranges on a store sign, then group them into tens to find the fruit total.
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Printable 1.NOS.E.10.b Worksheet
A ready-to-print activity worksheet aligned to 1.NOS.E.10.b, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- 2.NOS.C.8.a
Use strategies based on counting (e.g., counting on, counting back) and place value (e.g., partial sums, making tens, etc.) to add and subtract.
- 4.NOS.B.5.b
Use strategies based on place value (e.g., partial products) to multiply.
- 2.NOS.B.6.a
Use counting, make ten, and ten more/less, doubling strategies to add and subtract.
- 2.NOS.C.9.b
Use strategies based on place value (counting on, partial sums, making tens, etc.) to add and subtract.
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