time
adding
rounding
100

5 x 5 =

25

100

1 + 60

61

100

70 rounded by the nearest 100s

100

200

6 x 12 =

72

200

5 + 50 = 

55

200

100 rounded by the  nearest 10s

100

300

7x13

91

300

60 + 6

66

300

200  rounded by the  nearest 100s

200

400

80 x 3

240

400

50 + 12 

62

400

400 rounded by the nearest 10 

400

500

5 x 200

1000

500

60 + 60 =

120

500

500 rounded by the nearest 100s

500