# North Dakota - Grade 1 - Math - Numbers and Operations in Base Ten - Mental Math - 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.

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

### Keywords

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

## More North Dakota Topics

Compose two-dimensional shapes (rectangles, squares, trapezoids, triangles, half-circles, and quarter-circles) or three-dimensional shapes (cubes, right rectangular prisms, right circular cones, and right circular cylinders) to create a composite shape, and compose new shapes from the composite shape.1

Partition circles and rectangles into two and four equal shares, describe the shares using the words halves, fourths, and quarters, and use the phrases half of, fourth of, and quarter of. Describe the whole as two of, or four of the shares. Understand for these examples that decomposing into more equal shares creates smaller shares.

Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases: A. 10 can be thought of as a bundle of ten ones — called a “ten.” B. The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones. C. The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones).

Express the length of an object as a whole number of length units, by laying multiple copies of a shorter object (the length unit) end to end; understand that the length measurement of an object is the number of same-size length units that span it with no gaps or overlaps. Limit to contexts where the object being measured is spanned by a whole number of length units with no gaps or overlaps.

Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

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

• Grade Level 1
• State Test North Dakota State Assessment (NDSA)
• State Standards "North Dakota Math Content Standards North Dakota ELA Content Standards"
• Subject Math
• Topic Name Mental Math
• Standard ID 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.