## Elementary Technical Mathematics

$120\frac{3}{4}$ miles per hour
To find the average speed, divide the distance flown by the total travel time: Speed $\\=684\frac{1}{4} \div 5\frac{2}{3} \\=\frac{4(684)+1}{4} \div \frac{3(5)+2}{3} \\=\frac{2737}{4} \div \frac{17}{3}$ Use the rule $\frac{a}{b} \div \frac{c}{d} = \frac{[a}{b} \times \frac{d}{c}$ to obtain: $\\=\frac{2737}{4} \times \frac{3}{17} \\=\frac{2737(3)}{4(17)} \\=\frac{8211}{68} \\=120\frac{3}{4}$ The aircraft was flying at $120\frac{3}{4}$ miles per hour.