MULTIPLY!
MULTIPLY BY 10
MULTIPLY BY 11
ROUNDING to 100
SUBTRACT
100

5X5

25

100

10X4

40

100

11x1

11

100

121

100

100

50-10

40

200

10X10

100


200

10X3

30

200

11x4

44

200

211

200

200

40-30

10

300

11X4

44

300

10X5

50

300

11x5

55

300

365

400

300

100-50

50

400

6X7

42

400

10X7

70

400

11x6

66

400

489

500

400

76-10

66

500

9X9

81

500

10X8

80

500

11x8

88

500

685

700

500

525-25

500