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Skills Covered

Find how many more joined or are needed (change unknown)
Find how many went away (change unknown)
Find how many there were at first (start unknown)

Write a number sentence with the unknown in any place
Use a bar model for a start unknown story
Show a story as jumps on a number line

How to Use This Pack

Five pages of the add-to and take-from stories that are hardest for 1st graders: the ones where the question is not how many there are now. Page 1 asks how many more came or are needed (9 frogs on a log, some hop on, now there are 14). Page 2 asks how many went away (16 owls, some fly away, now there are 11). Page 3 asks how many there were at first, before more came, and page 4 how many there were at first, before some went away, with a bar model for each story. Page 5 mixes all four kinds on a number line. The key shows one number sentence for each story; a related fact, such as 12 − 8 = 4 for 8 + 4 = 12, is right too.

In the Classroom

Act out a change unknown story before page 1: put 8 counters in a cup, secretly add some more, then show 12. How many did I add? Ask students to say the story as a number sentence with a box for the unknown (8 + □ = 12) before solving. For the start unknown pages, cover the starting group with a cup so the "some" is really unknown.

At Home

Play "what did I start with?": put some coins in your hand, add 3 more, show your child the 10 you now have, and ask how many you started with. Let your child count on or back on the number line on page 5 and draw the jump.

Tips for Success

Find what you know and what you do not know before you add or subtract
How many more came? Count on from the start to the end: 8, 9, 10, 11, 12 is 4 more
How many at first, before some went away? Add back the ones that left
Check your answer by putting it back into the story

Common Core Standards Alignment

This pack supports the following Common Core State Standards for Mathematics:

1.OA.A.1 Solve story problems up to 20 that join, separate, combine or compare amounts, with the missing number in any spot, using objects, drawings or equations.
1.OA.A.2 Solve story problems where three numbers are added together for a total of 20 or less.
1.OA.B.4 Treat subtraction as finding a missing addend: to solve 12 - 9, ask what added to 9 makes 12.
1.OA.D.8 Solve for the missing number in adding or subtracting equations like 9 + ? = 15 or ? - 4 = 6.

Change Unknown and Start Unknown Word Problems

1st Grade

A 5-page change unknown and start unknown word problems pack for 1st grade, with numbers within 20. Find how many more came or are needed (Mia has 8 cookies, now she has 12), how many went away (Ben had 13 strawberries, now he has 6), and how many there were at first, before more came or before some went away. Write a number sentence for each story, use bar models for the start unknown stories, and show all four kinds on a number line. Every page comes in color and in black and white. Answer keys included.

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What’s Included

5 worksheets in color and in black and white, with answer keys (15 pages)
18 story problems and 5 worked examples, numbers within 20
Change unknown and start unknown stories, adding and taking away
Bar models and number lines with the jumps drawn on the key

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