Question 1134823

a motorist travelling at constant speed leaves A at 11 00 intending to arrive B , 100km away at 1300 . half an hour later one of the tyres are punctured ands he is delayed for 18 mins . how fast must he then proceed in order to reach B on time ? at what time will he meet a cyclist who leaves town B at 11 45 for A ., travelling at a contant speed of 20 km/h ? make a distancwe time graph
<pre>The other person's answer of 31.25 km/h can't be correct and just doesn't make sense.
 
With a time of 2 (1300  -  1100) hours to cover a distance of 100 km, his planned average-speed was {{{matrix(1,4, 100/2, or, 50, "km/h")}}} for the trip
At {{{matrix(1,6, 50, "km/h", and, 1/2, hour, later)}}}, distance covered was: {{{matrix(1,6, 50, "*", 1/2, "=", 25, km)}}}

{{{matrix(1,8, 18, minutes, "=", 18/60, hour, or, .3, hour)}}}
Since he has 1.2 (2 - .5  -  .3) hours to cover 75 (100  -  25) km, then his speed MUST be: {{{highlight_green(matrix(1,4, 75/1.2, "=", 62.5, "km/h"))}}}. 
**NOTE: He MUST travel FASTER than his planned average-speed in order to make it on time.