Grade 9 Time, Distance and Speed Notes With Examples

Last reviewed: 11 November 2026

Updated November 2026. These Grade 9 time, distance and speed notes show how to convert speed between km/h and m/s, how to find average speed, how velocity and acceleration are used in simple calculations, and how longitudes give local time around the Earth. Speed is distance travelled per unit time. If a matatu covers 72 km in one hour, its speed is 72 km/h, which is the same as 20 m/s.

The worked questions are original practice for Kenyan junior school learners, not an official paper. They follow the Grade 9 Mathematics measurements sub-strand on time, distance and speed in the KICD Grade Nine curriculum designs. The Integrated Science treatment of motion, with a different emphasis, is in the Grade 9 speed, velocity and acceleration notes. For the maths topic list, start with the Grade 9 maths revision guide and the Grade 9 notes hub.

On this page

1. Speed in km/h and m/s, and Average Speed
2. Velocity and Acceleration
3. Longitudes and Local Time
4. Original Practice Questions With Worked Answers
5. Frequently Asked Questions

Speed in km/h and m/s, and Average Speed

Speed = distance ÷ time. To change km/h into m/s, convert kilometres to metres and hours to seconds: divide by 3.6, or multiply by 5/18. To change m/s into km/h, multiply by 3.6, or by 18/5. OpenStax College Physics’s section on time, velocity and speed uses the same relationship between distance and time.

Average speed = total distance ÷ total time. It is not always the mean of the separate speeds, because each stretch may take a different time.

Worked example: converting units

A school bus travels at 72 km/h. In m/s this is 72 × (5/18) = 4 × 5 = 20 m/s.

A sprinter runs at 15 m/s. In km/h this is 15 × (18/5) = 3 × 18 = 54 km/h.

Worked example: average speed

A family drives 60 km to a market at 60 km/h, then returns the same 60 km at 30 km/h because of traffic. Total distance = 120 km. Time going = 1 hour; time returning = 2 hours; total time = 3 hours. Average speed = 120 ÷ 3 = 40 km/h, not 45 km/h. Adding the two speeds and dividing by two ignores the extra hour spent on the slower journey.

Velocity and Acceleration

Velocity is speed in a stated direction, so “20 m/s due north” is a velocity while “20 m/s” alone is a speed. Acceleration is the change in velocity divided by the time taken: a = (v − u) ÷ t, where u is the starting velocity and v is the finishing velocity. The same definition is used in OpenStax College Physics’s section on acceleration. In this mathematics sub-strand you work out acceleration from that relationship; you do not need the extra motion formulas used later in science.

Worked example

A bicycle speeds up from 10 m/s to 22 m/s in 4 seconds, in a straight line along a road. Acceleration = (22 − 10) ÷ 4 = 12 ÷ 4 = 3 m/s². If the bicycle slows from 22 m/s to 10 m/s in 4 seconds, the change is −12 m/s and the acceleration is −3 m/s², a deceleration.

Longitudes and Local Time

The Earth turns through 360° in 24 hours, so it turns 15° every hour, or 1° every 4 minutes. Places to the east see the sun earlier and have a later local time; places to the west have an earlier local time. NOAA’s explainer on longitude describes longitude as the east–west position measured from the prime meridian.

• Time difference in hours = (difference in longitude) ÷ 15.
• Time difference in minutes = (difference in longitude) × 4.
• Add the difference when you move east; subtract it when you move west.

Worked example: towns on the same date

Town A lies at 30°E and Town B at 15°E. The difference is 15°, which is 1 hour. A is further east, so when it is 10:00 in B it is 11:00 in A.

Town C is at 40°W and Town D at 20°E. The longitudes are on opposite sides of the prime meridian, so the difference is 40° + 20° = 60°, which is 4 hours. D is east of C, so D is ahead. When it is 08:00 in C it is 12:00 in D.

Original Practice Questions With Worked Answers

1. Change 90 km/h to m/s. 90 × (5/18) = 25 m/s.
2. Change 12.5 m/s to km/h. 12.5 × (18/5) = 2.5 × 18 = 45 km/h.
3. A runner covers 400 m in 50 s, rests, then covers another 200 m in 30 s. Find the average speed for the 600 m, ignoring the rest. Total time moving = 80 s. Average speed = 600 ÷ 80 = 7.5 m/s.
4. A car increases its velocity from 15 m/s to 27 m/s in 6 s. Find the acceleration. (27 − 15) ÷ 6 = 2 m/s².
5. Town P is at 10°E and Town Q at 35°E. If local time in P is 09:20, what is the local time in Q? Difference = 25° = 100 minutes = 1 h 40 min. Q is east, so the time is 11:00.
6. A learner says average speed is always the mean of the two speeds. Give a counter-example. The 60 km at 60 km/h and 60 km at 30 km/h journey above has average speed 40 km/h, not 45 km/h.

Cover the answers and work each question before checking. For timed practice, use the Grade 9 revision papers or the Grade 9 CBC Challenge. These notes are free; full revision access is available with the KSh 20 Day Pass or the KSh 500 Monthly Pass.

Frequently Asked Questions

How do you convert km/h to m/s?

Multiply by 5/18, or divide by 3.6. That turns kilometres into metres and hours into seconds in one step, so 72 km/h becomes 20 m/s.

What is the difference between speed and velocity?

Speed is how fast something moves. Velocity is speed with a direction, such as 20 m/s due north. Two vehicles can have the same speed and opposite velocities if they travel opposite ways along a road.

How is local time found from longitude?

The Earth turns 15° each hour, or 1° every 4 minutes. Find the difference in longitude, convert it to time, then add it when travelling east and subtract it when travelling west.

Why is average speed not always the mean of the speeds?

Average speed uses total distance and total time. If you spend longer at the slower speed, that stretch has more weight, so the average is pulled below the midpoint of the two speeds.