How do you use the distributive property to rewrite and evaluate #5*89#?

Question

1920 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-09-18T09:09:55

Write 89 as an addition or subtraction using a multiple of 10.

#445#

This is SUCH a nifty technique and one you can use in mental calculations to make things quicker and easier -and probably more accurate too.

No-one knows the 89 times table! Rewrite 89 in a different form.

#5 xx color(red)(89)#

= #5xxcolor(red)((90-1))" "larr# use the distributive law

=#450-5#

= #445#

OR

#5 xx color(red)(89)#

= #5xxcolor(red)((80+9))" "larr# use the distributive law

=#400+45#

=#445#