Five pages of strategies for adding and subtracting within 1,000. Page 1 makes a hundred: a number bond splits one number so that the other becomes a hundred (398 + 145: 398 + 2 = 400, and 400 + 143 = 543). Page 2 uses a friendly number: add or take away the next hundred, then fix the answer (503 − 198: 503 − 200 = 303, and 303 + 2 = 305). Page 3 counts up on an open number line from the number taken away: to the next hundred, then the hundreds, then the rest (612 − 387: 13 + 200 + 12 = 225), and checks by adding. Page 4 adds three numbers in an easier order (270 + 30 first), then has four problems to solve any way, with room to show the work; the key shows one way for each. Page 5 adds and subtracts four-digit numbers in columns, regrouping in one, two or three places and trading across zeros (4,005 − 1,738); it is for the states whose 3rd grade standards include four-digit numbers (Florida, Georgia and Oklahoma), and makes a good stretch elsewhere. The first problem on each page is worked as an example.
Do one problem from each page as a number talk before students work: write 398 + 145 on the board and ask for different ways to find it. On page 4, have students compare the ways they chose and say why one was quicker.
Practice the strategies with prices: a $398 bike and a $145 helmet. Ask how making $400 first helps, or how taking away $200 helps find $503 − $198.
This pack supports the following Common Core State Standards for Mathematics:
© Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
Mental math strategies for adding and subtracting within 1,000, then four-digit numbers in columns. Students make a hundred, use a friendly number and fix the answer, count up on an open number line, add in an easier order, and regroup in four-digit sums and differences.
Tell us what to make next, or build your own with a worksheet maker.
This worksheet is free to download, print, copy, and hand out in your classroom or at home. You do not need to create an account, and there are no watermarks on the PDF.
