Big Ideas Math Chapter 2

Doubles -/+ 1

100

2+3

2+2=4 or 3+3=6

so, 2+3=5

200

5+6

5+5=10 or 6+6=12

so, 5+6=11

300

8+7

8+8=16 or 7+7=14

so, 8+7=15

400

20+21

20+20=40

so, 20+21=41

500

400+399

400+400=800

so, 400+399=799

Make a 10

100

7+6

7+3=10 and 10+3=13

200

5+8

5+5=10 and 10+3=13

300

9+7

9+1=10 and 10+6=16

400

13+9

13+7=20 and 20+2=22

500

58+7

58+2=60 and 60+5=65

Get to 10

100

12-5

12-2=10 and 10-3=7

200

13-6

13-3=10 and 10-3=7

300

9+4=_+10

9+3=14 so 14-10=4

400

25-9

25-5=20 and 20-4=16

500

225-27

225-25=200 and 200-2=198

Fact Families

100

6+_=10

10-6=4

200

_+5=13

13-5=8

300

17-_=10

17-10=7

400

_-24=30

30-24=6

500

245-_=200

245-200=45

Word Problems

100

Some friends are at a skating rink.  6 more join them. Now there are 11.  How many friends were there to start?

_+6=11

5

200

A box has 18 toys.  There are 5 barbies and 6 superheroes.  The rest are lego minifigs.  How many minifigs are there?

_+5+6=18

so 18-11=7

300

There are 9 fewer students at the library than at the park.  There are 7 students at the library.  There are 6 students at the pool.  How many students are at the park?

9+7=16

The number of students at the pool doesn't matter.

400

There are 6 birds and 3 squirrels in a tree.  4 birds fly away.  How many animals are in the tree in all?

6+3=9 and 9-4=5

500

You have 9 markers.  Your friend has 2 fewer than you.  How many markers are there in all?  

9-2=7 and 7+9=16