You measure the open distance between the floor and the bottom surface of the gas pedal. Then you press the gas pedal down 1/2 of that distance.
The product of speed and time is distance. To calculate the total distance you multiple the speed in kilometers per second by the time at that speed in seconds, do this for all 3 different speeds then add them up, the 17.4 minutes eating does not affect the answer at all. to convert from minutes to seconds multiply time in minutes by 60, to convert from km/h to km/s divide km/h by 3600.
(23.5x60)x(74.5/3600) = 29.2km (rounded to 1 decimal place)
+
(15.9x60)x(111/3600) = 29.4km (rounded to 1 decimal place)
+
(49.2x60)x(38.7/3600) = 31.7km
=90.3km
The brackets are not necessary but i think it makes it more clear what is happening in your working.
