adding and subtracting

doubles

100

What is 20 plus 20?

40

200

What is 300 plus 300?

600

300

What is 4000 plus 4000?

8000

400

What is 12 plus 12?

24

500

What is 600 plus 600?

1200

adding

100

123+9

132

200

82+6

88

300

258+10

268

400

66+9

75

500

1057+4

1061

subtracting

100

93-9

84

200

158-11

147

300

86-12

74

400

23-4

19

500

74-15

59

adding and subtracting

100

259-10

249

200

600-15

585

300

24+24

48

400

999-8

991

500

864-40

824