Question 1144190

Alex's bike ride to work usually takes 22 minutes at 9 kph. One morning he found a new bike route that was 5 minutes faster. If he decides to use this new route again and wants to reach home by an additional 2 minutes earlier, how fast should he cycle?
<pre>Since new route takes 5 minutes less, then time using new route = 22  -  5 = 17 mins, or {{{matrix(1,4, 17/60, of, an, hour)}}}
Since he apparently biked the same speed on the new route, then new route’s distance = {{{matrix(1,6, (17/60)(9), "=", (17/20)(3), "=", 51/20, km)}}}
To get home 2 minutes earlier, his time on new route must be 17  -  2 = 15 mins, or {{{matrix(1,6, 15/60, "=", 1/4, of, an, hour)}}}
Then, his speed to accomplish this task is: {{{highlight_green(matrix(1,8, (51/20)/(1/4), "=", (51/20) * 4, "=", 51/5, or, 10&1/5, "km/h  "))}}}