The bicylist rode 4.5 miles in 18 minutes. To convert 4.5 miles in 18 minutes we can divide 60( 1 hour) by 18 which is 10/3 , and multiply it by 4.5 miles: 4.5(10/3) miles in 18(10/3) minutes = 15 miles/h Which means that he rode at a speed of 15 miles/h for 18 minutes Then he rode 7.5 miles in 30 minutes which means he rode at an avarage speed of 15 miles/h for half an hour. 7.5(2) miles in 30(2) minutes
Now to find the avarage of 15 miles/h for 18 minutes 15 miles/h for half an hour As both speeds are the same the average is 15 miles an hour I hope you understood my brief explanation