Question

Tom found two wooden planks. One was 3 1/4 feet long and the second was 4 3/8 feet long. He used 5 feet of them for a project. How much is left over?

Answer 1

let's firstly convert the mixed fractions to improper fractions.

$\bf \stackrel{mixed}{3\frac{1}{4}}\implies \cfrac{3\cdot 4+1}{4}\implies \stackrel{improper}{\cfrac{13}{4}}~\hfill \stackrel{mixed}{4\frac{3}{8}}\implies \cfrac{4\cdot 8+3}{8}\implies \stackrel{improper}{\cfrac{35}{8}} \\\\[-0.35em] ~\dotfill$

$\bf \stackrel{\textit{first one}}{\cfrac{13}{4}}+\stackrel{\textit{second one}}{\cfrac{35}{8}}-\stackrel{\textit{were used}}{5}\implies\cfrac{13}{4}+\cfrac{35}{8}-\cfrac{5}{1}\implies \stackrel{\textit{using an LCD of 8}}{\cfrac{(2)13~+~(1)35~+~(8)5}{8}} \\\\\\ \cfrac{26+35-40}{8}\implies \cfrac{21}{8}\implies 2\frac{5}{8}$