Since Cindy used 1/10 of a metre of ribbon to make just one decoration that she obtained by dividing 3/10 of a meter of ribbon into equal parts, then we can calculate the number of decorations that Cindy made. In this scenario, all we need is an idea on how to divide fractions and we are good to go.
If Cindy used 1/10 of a metre obtained by dividing 3/10 of a metre of ribbon to make decorations, then the number of decorations she made can be gotten by dividing 3/10 by 1/10
i.e 3/10 ÷ 1/10
= 3/10 × 10/1
= 3 decorations.
That is she used 1/10 + 1/10 + 1/10 = 3/10 to make (3 decorations).
So as you can see if you multiply the numerator(top) and the denominator(bottom) by the same number, you get an equivalent fraction! In my example you can see that I multiplied both by 2.