How do you simplify 4(0.2m-0.3n)-6(0.7m-0.5n)?

1 Answer
Jan 28, 2017

I have elected to solve this way to try and get you thinking about numbers differently.

3.4m-4.7n

Explanation:

color(blue)("Introduction to the idea behind the method")

Using actual number to prove my point:

Suppose we had 1/2. This is the same as 5/10

Which is the same as 1/10xx5

Which is the same as 1/10(3+2)
This is called 'distributive' property in that the 'multiply by 1/10' is distributed over both the 3 and the 2. So we have:
(1/10xx3)+(1/10xx2)

Which is the same as (0.3+0.2)=0.5=1/2
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color(blue)("Answering the question")

Given:" "4(0.2m-0.3n)-6(0.7m-0.5n)

Don't like decimals so lets get rid of them

Write as:color(white)(2/2.)4/10(2m-3n)-6/10(7m-5n)larr" distributive"

Same as 1/10[color(white)(2/2) 4(2m-3n)-6(7m-5n)color(white)(2/2)]

" "1/10[color(white)(2/2)8m-12n-42m-35ncolor(white)(2/2)]

" "1/10[color(white)(2/2)-34m-47ncolor(white)(2/2)]

" "3.4m-4.7n