Compensation

We learned in class today to multiply using compensation.  Compensation is a way to multiply 2 digit numbers. 

Ask your students...

Can they complete their homework using compensation?


Here is an example:

4 x 19 = ----4 x 20 = 80
                    4 x 1   =   4

20 is bigger than 19 so we subtract 80-4 = 76

So... 4 x 19 = 76

4 x 21 = --------4 x 20 = 80
                          4 x   1 =   4

20 is smaller than 21 so we add 80 + 4 =84

So....4 x 21 = 84


Here is one more example:

195 x 5 =--------200 x 5 = 1000
                             5  x 5  =     25

200 is bigger than 195 so you subtract---1000-25=975

So.....195 x 5 = 975