Time and Temperature

Grade 7 Math: Time and Temperature

Lesson Objectives

Read and interpret time on both 12-hour and 24-hour clocks.
Convert between hours, minutes, and seconds.
Understand and compare temperatures in degrees Celsius and Fahrenheit.
Perform basic calculations involving time intervals.
Apply time and temperature concepts to real-life situations.

Lesson Introduction

Time and temperature are part of our daily lives. We check the time to keep appointments and plan our day, and we look at the temperature to decide what to wear or whether to turn on a fan or heater. In this lesson, you will learn how to read and work with both time and temperature.

Core Lesson Content

Reading Time

Time can be read using either the 12-hour clock or the 24-hour clock.

Example: 1:00 PM in 12-hour clock is $13:00$ in 24-hour clock.

Converting Time Units

There are: $1 \text{ hour} = 60 \text{ minutes}$ , and $1 \text{ minute} = 60 \text{ seconds}$ .

Understanding Temperature

Temperature can be measured in degrees Celsius ( $^\circ C$ ) or Fahrenheit ( $^\circ F$ ). To convert:

$^\circ F = \left( \frac{9}{5} \times ^\circ C \right) + 32$
$^\circ C = \frac{5}{9}(^\circ F - 32)$

Worked Examples

Example 1: Convert 150 minutes into hours and minutes.

150 \div 60 = 2 \text{ hours and } 30 \text{ minutes}

Example 2: Convert 5:45 PM to 24-hour time.

5 + 12 = 17

So, the time is

17:45

Example 3: What is the time difference between 9:15 AM and 2:45 PM?

2:45 - 9:15 = 5 \text{ hours and } 30 \text{ minutes}

Example 4: Convert 25°C to Fahrenheit.

F = \left( \frac{9}{5} \times 25 \right) + 32 = 77^\circ F

Example 5: Convert 95°F to Celsius.

C = \frac{5}{9}(95 - 32) = 35^\circ C

Example 6: If a train leaves at 10:20 and arrives at 13:05, how long was the journey?

13:05 - 10:20 = 2 \text{ hours and } 45 \text{ minutes}

Example 7: Add 2 hours 35 minutes and 1 hour 50 minutes.

2h 35m + 1h 50m = 4h 25m

Example 8: The temperature at 7 AM is 16°C and at 2 PM it is 28°C. What is the change?

28 - 16 = 12^\circ C \text{ increase}

Example 9: Subtract 45 minutes from 3 hours.

3h = 180m, \quad 180 - 45 = 135m = 2h 15m

Example 10: Convert 2.5 hours into minutes.

2.5 \times 60 = 150 \text{ minutes}

Exercises

Convert 200 minutes into hours and minutes. $...$
[JAMB] What is 3:30 PM in 24-hour format? $...$ [Past Question]
Convert 40°C into Fahrenheit. $...$
Convert 104°F into Celsius. $...$
[WAEC] What is the time difference between 8:20 AM and 1:15 PM? $...$ [Past Question]
A show started at 7:50 PM and ended at 10:10 PM. How long did it last?
[NECO] A person works from 9:00 AM to 4:30 PM. How long does he work? [Past Question]
If a room temperature is 20°C, what is it in Fahrenheit?
[NABTEC] Find the difference between 3 hours and 100 minutes. $...$ [Past Question]
Add 1h 45m to 2h 50m. $...$

Conclusion/Recap

In this lesson, you have learned how to read and convert time, understand temperature scales, and solve related problems. Up next, we’ll be learning about measurement units such as length, mass, and capacity.