Math Strategies - Operations / Mental Math

Adding

100

34+17=?

51

200

2/5+3/5=?

5/5 or 1

300

1/6+4/5=?

29/30

400

4.5+7.3=?

11.8

500

25+x=50

25

Subtracting

100

85-12=?

73

200

4/5-2/5=?

2/5

300

7/8-3/4=?

1/8

400

73.1-5.6=?

67.5

500

10-x=25

x=-15

Multiplying

100

3xx7=?

21

200

3/4xx2/4=?

6/16 or 3/8

300

2/7xx9/4=?

18/28 or 9/14

400

2.8xx6.2=?

17.36

500

4x=16

x=4

Dividing

100

45-:5=?

9

200

1/5-:5/1=?

1/25

300

7/5-:2/3=?

21/10 or 2 1/10

400

5.2/0.5=?

10.4

500

x/7=7

x=49