Question

how to solve, A reservoir is 3 1/4 miles wide. Tony sails 4/5 the width of the reservoir. About how far did Tony sail?

Answer 1

Well, how much is 4/5 of 3 and 1/4?  well, is just their product, thus, firstly, let's change the mixed fraction to "improper" and proceed,

$\bf \stackrel{mixed}{3\frac{1}{4}}\implies \cfrac{3\cdot 4+1}{4}\implies \stackrel{improper}{\cfrac{13}{4}}\\\\ -------------------------------\\\\ \cfrac{4}{5}\cdot \cfrac{13}{4}\implies \cfrac{13}{5}\implies 2\frac{3}{5}$