This document discusses units of time measurement and converting between units. The SI units for time are seconds, minutes, hours, days, months, and years. Short durations are measured in seconds, minutes, and hours, while longer durations are measured in days, weeks, months, and years. Conversion examples show how to change between units like minutes to seconds, hours to minutes, days to hours, weeks to days, and months to years. The document also covers distance, time, and speed calculations using the formula D=S×T where distance equals speed times time.

1. TIME

2. SI Units
We measure time using different units,
depending on the duration of the event.
Shorter durations are measured in seconds,
minutes and hours. Longer durations are
measured in days, weeks, months and years.
The units of time are related to each other. The
SI units used for time are seconds, minutes,
hours, days, months, and years.

3. Time Conversion Table
Conversion Example
Minutes to Seconds 1 minute = 60 seconds 25 minutes = 60 × 25 = 1500 seconds
Hours to Minutes 1hour = 60 minutes 5h = 5 × 60 = 300 mins
Days to hours 1 day = 24 hours 10 days = 10 × 24 hours = 240 hours
Weeks to days 1 week =7days 5 weeks = 5 x 7 = 35 days
Month to weeks 1 month = 4 weeks 8 months = 8 × 4 weeks = 32 weeks
Year to Months 1 year =12 months 3 years = 3 × 12 months = 36 months

4. Converting Smaller Units to Larger Units
For Example
1.Convert 220 minutes to hours and minutes.
Solution:
We know that 60 minutes = 1 hour
220 minutes = (220/60) hours
So, 220 mins = 3 hrs. 40 mins
2. How many weeks are there in 21 days?
Answer: 21 days ÷ 7 days = 3 weeks
3. If a task takes 360 hours to complete, how many days is that equivalent to?
Answer: 360 hours ÷ 24 hours = 15 days
Note: To convert smaller units to larger units, we divide .

5. Word Problems Involving Time
Example 1
Mary left home at 2:15 p.m. and returned at 3:05 p.m. How long was she
away from home?
Solution:
Example 2
A boat leaves at 05.35 and arrives at 18.20. How long is the journey?
Solution:
Note: Again, 20–35 is not
meaningful in the context
of time, so carry one hour
over to give 17 h 80 min.

6. Distance, Time & Speed
Speed is a measure of how quickly a body moves from one place to
another place. The speed of a body is the distance covered by the
body in unit time.
Distance is the movement of an object in any particular direction.
Time can be defined as the duration in which an object covers a
given distance.

7. Units of Measure for Distance, Time & Speed
The units of measurement of distance are kilometre (km),
meter (m), centimetre (cm), and millimetre (mm).
The units of measurement of time are an hour (h), minute
(min), and second (sec).
The units of measurement of speed are kilometres per
hour (km/h), a minute per second (min/sec), centimetre
per second (cm/sec), and millimetre per second (mm/sec).

8. Formula to Calculate
Distance, Time & Speed
An easy way to remember the formula for speed (S), distance (D),
and time (T) is by using a magic triangle.
D
S T

9. Calculating Distance
D
S T
Cover the shaded part of the triangle with your
fingers. What letters can you see? Letters S
and T are next to each other which means
multiplication. So, we can say that the formula
for calculating distance is D = S × T
D = S x T
Example: Calculate the distance that you will travel if you
drive for 4 hours at 80 km/h.
D = S × T
= 80 km/h × 4h
= 320 km

10. Calculating Speed
D
S T
Cover the shaded part of the triangle with your
fingers. What letters can you see? Since D is
over T, it means division, so we can derive the
formula of speed as:
Speed = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 ÷ 𝑡𝑖𝑚𝑒 or 𝑺 =
𝑫
𝑻
S = D ÷ T
Example: Mr. Jones drives his van and travels 80km in 2
hours. Find the speed at which he drove.
S = D ÷ T
= 80 ÷ 2
= 40 km/h

11. Calculating Speed
D
S T
Cover the shaded part with your fingers . What
letters can you see? D is over S, so we can
derive the formula for time as distance divided
by speed.
Time = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 ÷ speed 𝑻 =
𝑫
𝑺
T = D ÷ S
Example: How long does it take to travel 180 kilometers at 45 km/h?
T = D ÷ S
= 180 ÷ 45
= 4 hours