Question

A Robin can fly 10 miles per hour faster than a blue jay .It takes a Robin 1 1/2 hours to fly 45 mileshow many hours will it take a blue hay to fly that same distance

Answer 1

$\begin{gathered} \text{let:} \\ vr=\text{robin speed} \\ vb=\text{blue jay speed} \\ vr=vb+\frac{10mi}{h} \\ vb=vr-\frac{10mi}{h} \end{gathered}$

It takes a Robin 1 1/2 hours to fly 45 miles:

$\begin{gathered} d=v\cdot t \\ 45=vr\cdot t \\ 45=vr\cdot1.5 \\ vr=\frac{45}{1.5} \\ vr=\frac{30mi}{h} \end{gathered}$

Since:

$\begin{gathered} vb=vr-\frac{10mi}{h} \\ vb=\frac{20mi}{h} \end{gathered}$$\begin{gathered} t=\frac{d}{v} \\ t=\frac{d}{vb} \\ t=\frac{45}{20} \\ t=2.25h \end{gathered}$