Multiply by 10s
80 x 10 =
800
17 x 28 =
20 x 30 = 600
13 x 19 =
247 (show model)
40 x 38 =
1,520
27 x 34 = 27 x (30 + 4)
= (27 x 30) + (27 x 4)
= (20 + 7) x ______ + (20 + 7) x _____
= (20 x ___) + (7 x ___) + (30 x ____) + (7x__)
= _____ + _____ + _____ + ______
= ______
30 x 60 =
1800
42 x 81 =
40 x 80 = 3,200
21 x 36 =
756
(show model)
13 x 21 =
273
43 x 18 = 43 x (10 + 8)
= (43 x 10) + (43 x 8)
= (40 + 3) x ______ + (40+ 3) x _____
= (40 x ___) + (3 x ___) + (40 x ____) + (3x__)
= _____ + _____ + _____ + ______
= ______
50 x 20 =
1000
25 x 74 =
30 x 70 = 2100
73 x 46 =
3,358
62 x 34 =
2,108
70 x 11 =
770
Write factors that could be estimated to equal
400
___ x ____
^ ^
___ x ____ = 400
39 x 84 =
3,276
(show model)
73 x 45 =
3,285
40 x _____ = 3,200
80
Write factors that could be estimated to equal
8,100
___ x ____
^ ^
___ x ____ = 8,100
Find the missing digits
__2
x __5
--------
300
60
50
+10
----------
________
1 2
__
3 5
__
78 x 66 =
5,148