Question

Bill and Amy want to ride their bikes from their neighborhood to school which is 14.4 kilometers away,It takes Amy 40 minutes to arrive at school.Bill arrives 20 minutes after Amy.How much faster (in meters/second) is Amy's average speed for the entire trip?

Answer 1

First you must calculate the speed of Amy and speed of Bill.

$d=14.4km=14400m \\t_a=40min=2400sec \\t_b=20min=1200sec \\s_a=\frac{d}{t_a}=\frac{14400m}{2400sec}=\boxed{6\frac{m}{sec}} \\s_b=\frac{d}{t_b}=\frac{14400m}{1200sec}=\boxed{12\frac{m}{sec}}$

Now calculate the difference between Bill's speed and Amy's speed.

$\Delta{s}=s_b-s_a=12\frac{m}{sec}-6\frac{m}{sec}=\boxed{6\frac{m}{sec}}$

Amy's average speed is not faster. Bill's average speed is faster than Amy's by 6 m/sec.

Hope this helps.

r3t40