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Python Program to Calculate Speed, Distance and Time

Beginner · Basics

Speed, distance and time are linked by one formula: speed = distance / time. Rearranged, it also gives distance = speed x time and time = distance / speed, and this program uses it all three ways.

Program

speed_distance_time.py
# 1. Speed from distance and time
distance = 150 # in km; or: distance = float(input("Enter distance in km: "))
hours = 2.5 # in hours; or: hours = float(input("Enter time in hours: "))
speed = distance / hours
print(f"Speed = {distance} km / {hours} h = {speed} km/h")
# 2. Distance from speed and time
speed = 60 # km/h
hours = 3
print(f"Distance = {speed} km/h x {hours} h = {speed * hours} km")
# 3. Time from distance and speed
distance = 225 # km
speed = 90 # km/h
hours = distance / speed
whole_hours = int(hours)
minutes = round((hours - whole_hours) * 60)
print(f"Time = {distance} km / {speed} km/h = {hours} h, or {whole_hours} h {minutes} min")
Output
Speed = 150 km / 2.5 h = 60.0 km/h
Distance = 60 km/h x 3 h = 180 km
Time = 225 km / 90 km/h = 2.5 h, or 2 h 30 min

How it works

  1. Speed is distance divided by time, so 150 km in 2.5 hours is 60 km/h.
  2. Multiplying speed by time gives the distance covered: 60 km/h for 3 hours is 180 km.
  3. Dividing distance by speed gives the time taken: 225 km at 90 km/h is 2.5 hours.
  4. int(hours) keeps the whole hours, and the leftover part times 60 gives the minutes, so 2.5 hours prints as 2 h 30 min.

Other ways to write it

One function that finds the missing value

One function that finds the missing value
def solve(speed=None, distance=None, hours=None):
if speed is None:
return f"speed = {distance / hours:.2f} km/h"
if distance is None:
return f"distance = {speed * hours:.2f} km"
return f"time = {distance / speed:.2f} h"
print(solve(distance=150, hours=2.5))
print(solve(speed=60, hours=3))
print(solve(speed=90, distance=225))
Output
speed = 60.00 km/h
distance = 180.00 km
time = 2.50 h

Keyword arguments with a default of None let you leave out whichever value is unknown, and the function works out that one.

Converting km/h to m/s

Converting km/h to m/s
speed_kmh = 72
speed_ms = speed_kmh * 1000 / 3600 # 1 km = 1000 m, 1 h = 3600 s
print(f"{speed_kmh} km/h = {speed_ms} m/s")
print(f"Shortcut: {speed_kmh} x 5/18 = {speed_kmh * 5 / 18} m/s")
Output
72 km/h = 20.0 m/s
Shortcut: 72 x 5/18 = 20.0 m/s

Physics problems often need meters per second; multiplying by 1000 / 3600, which simplifies to 5/18, does the conversion.

Try it yourself

Find the average speed for a trip of 120 km in 2 hours followed by 180 km in 4 hours.

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