9514 1404 393
Answer:
(5 15/20) -(2 8/20) = 3 7/20
Step-by-step explanation:
Problems in "least common denominator" are made much easier if you are familiar with your times tables.
When you compare the denominator 4 to the denominator 20, you see that ...
20 = 5 × 4
An equivalent fraction is made by multiplying by 1. Here, the version of 1 you want for the top fractions is 5/5.
[tex]\dfrac{3}{4}= \dfrac{3}{4}\cdot\dfrac{5}{5}=\dfrac{3\cdot5}{4\cdot5}=\dfrac{15}{20}[/tex]
Similarly, the bottom fraction has its denominator multiplied by 4 to get from 5 to 20. The equivalent fraction is found by multiplying the numerator by the same number.
[tex]\dfrac{2}{5}=\dfrac{2\cdot4}{5\cdot4}=\dfrac{8}{20}[/tex]
Then the desired difference is ...
[tex]5\dfrac{15}{20}-2\dfrac{8}{20}=(5-2)+\left(\dfrac{15-8}{20}\right)=3\dfrac{7}{20}[/tex]
