# North Carolina - Grade 1 - Math - Numbers and Operations in Base Ten - Mental Math - NC.1.NBT.5

### Description

Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.

### Additional Info

• State - North Carolina
• Standard ID - NC.1.NBT.5
• Subjects - Math Common Core
• Grade - 1

### Keywords

• Math
• North Carolina grade 1
• Numbers and Operations in Base Ten

## More North Carolina Topics

Represent and solve addition and subtraction word problems, within 20, with unknowns, by using objects, drawings, and equations with a symbol for the unknown number to represent the problem, when solving: • Add to/Take from-Change Unknown • Put together/Take Apart-Addend Unknown • Compare-Difference Unknown

Measure lengths with non-standard units. • Express the length of an object as a whole number of non-standard length units. • Measure by laying multiple copies of a shorter object (the length unit) end to end (iterating) with no gaps or overlaps.

NC.1.OA.4 Solve an unknown-addend problem, within 20, by using addition strategies and/or changing it to a subtraction problem. NC.1.OA.6 Add and subtract, within 20, using strategies such as counting on, making ten, decomposing a number leading to a ten, using the relationship between addition and subtraction, using a number line, and creating equivalent but simpler or known sums. NC.1.OA.9 Demonstrate fluency with addition and subtraction within 10.

NC.1.OA.7 Apply understanding of the equal sign to determine if equations involving addition and subtraction are true. NC.1.OA.8 Determine the unknown whole number in an addition or subtraction equation involving three whole numbers.

Understand that the two digits of a two-digit number represent amounts of tens and ones. • Unitize by making a ten from a collection of ten ones. • Model the numbers from 11 to 19 as composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones. • Demonstrate that the numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens, with 0 ones.

## Here is the skill that North Carolina requires you to master

• Grade Level 1
• State Test End-of-Grade test
• State Standards North Carolina’s Standard Course of Study
• Subject Math
• Topic Name Mental Math
• Standard ID NC.1.NBT.5
• Description
Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.

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Education Galaxy helps students master North Carolina’s Standard Course of Study to prepare students for the End-of-Grade test administered by North Carolina Schools. Education Galaxy’s preparation program provides online assessment and practice for students in Grades K-6 to help build mastery towards North Carolina’s Standard Course of Study. Our unique online program is easy to use and enjoyable for both teachers and students. Students work on their Study Plans practicing important concepts while teachers pull formative assessment reports to identify the strengths and weaknesses of their classroom and individual students.