by what rational should we multiply -5/9 to get 1/5?
To do this, think of a similar problem using whole numbers instead of
fractions and how you would do it.
For instance, think of this problem:
By what number should we multiply 23 to get 161?To find that answer we divide 161÷23 and get 7.
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In your problem:
By what rational should we multiply -5/9 to get 1/5?the -5/9 corresponds to the 23 and the 1/5 corresponds to the 161.
So since in the other problem we divided 161÷23, in this problem
we divide the corresponding things the same way:
=
To divide by a fraction, we invert the fraction we are dividing by,
and change division to multiplication:
= 
Edwin
