Lesson Notes By Weeks and Term v5 - Grade 5
Time, temperature and everyday measurement problems – Week 6 focus
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Time, temperature and everyday measurement problems – Week 6 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Mathematics
Class: Grade 5
Term: 3rd Term
Week: 6
Theme: General lesson support
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This week, we're diving into time, temperature, and solving everyday measurement problems. These are essential skills that we use every single day, whether we're catching the Putco bus, cooking pap and vleis for dinner, or checking the weather forecast on SABC news to decide what to wear to school. Understanding time helps us manage our schedules and be punctual. Knowing about temperature helps us understand the weather and stay comfortable. And being able to measure accurately is crucial for everything from building a shack to sharing a loaf of bread fairly with our siblings. These skills empower us to navigate our daily lives with confidence and understanding.
Time Elapsed Time: This is the amount of time that passes between a start time and an end time.
Analogue Clocks: Remember that the short hand tells us the hour, and the long hand tells us the minutes. Each number on the clock represents 5 minutes.
Digital Clocks: Digital clocks show the time directly in hours and minutes, separated by a colon (:). 24-hour Time: This system avoids AM/P
M. For example, 2 PM is 14:00 in 24-hour time. This is used in many official schedules like train timetables.
Calculating Elapsed Time: We can use various methods to calculate elapsed time, including counting forward on a clock or timeline, subtracting times (remembering to borrow 60 minutes when necessary), or using mental math.
Example 1: Calculating Elapsed Time using a Timeline A taxi ride from Soweto to Johannesburg starts at 7:15 AM and ends at 8:50 A
M. How long did the taxi ride take?
Step 1: Draw a timeline.
Step 2: Mark the start time (7:15 AM) and the end time (8:50 AM) on the timeline.
Step 3: Calculate the time from 7:15 AM to 8:00 A
M. This is 45 minutes.
Step 4: Calculate the time from 8:00 AM to 8:50 A
M. This is 50 minutes.
Step 5: Add the two time intervals together: 45 minutes + 50 minutes = 95 minutes.
Step 6: Convert 95 minutes to hours and minutes: 95 minutes = 1 hour and 35 minutes.
Answer: The taxi ride took 1 hour and 35 minutes.
Example 2: Calculating Elapsed Time by Subtraction A soccer match starts at 3:30 PM and ends at 5:15 P
M. How long did the match last?
Step 1: Write down the end time (5:15 PM) and the start time (3:30 PM).
Step 2: Subtract the minutes: 15 minutes - 30 minutes. Since we can't subtract 30 from 15, we need to borrow 1 hour from the hours.
Step 3: Borrowing 1 hour (60 minutes) from 5 hours leaves us with 4 hours. Add the 60 minutes to the 15 minutes, giving us 75 minutes.
Step 4: Now subtract the minutes: 75 minutes - 30 minutes = 45 minutes.
Step 5: Subtract the hours: 4 hours - 3 hours = 1 hour.
Answer: The soccer match lasted 1 hour and 45 minutes. Temperature Celsius Scale (°C): This is the standard unit of temperature used in South Africa.
Reading a Thermometer: Look at the top of the liquid (usually red or blue) in the thermometer. The number next to the top of the liquid is the temperature.
Temperature Changes: Temperature can increase (rise) or decrease (fall). We use positive numbers to represent increases and negative numbers to represent decreases.
Example 1: Reading a Thermometer The thermometer shows a temperature of 28°
C. This is a warm day in Durban!
Example 2: Temperature Change The temperature in Johannesburg is 5°C in the morning. By midday, it rises by 12°
C. What is the temperature at midday?
Step 1: Start with the initial temperature: 5°
C. Step 2: Add the temperature rise: 5°C + 12°C = 17°
C. Answer: The temperature at midday is 17°
C. Example 3: Negative Temperature Change The temperature in Sutherland is 2°
C. Overnight, it drops by 8°
C. What is the temperature overnight?
Step 1: Start with the initial temperature: 2°
C. Step 2: Subtract the temperature drop: 2°C - 8°C = -6°
C. Answer: The temperature overnight is -6°
C. Measurement Length: We use millimeters (mm), centimeters (cm), meters (m), and kilometers (km) to measure length. 10 mm = 1 cm, 100 cm = 1 m, 1000 m = 1 km.
Mass: We use grams (g) and kilograms (kg) to measure mass. 1000 g = 1 kg.
Capacity/Volume: We use milliliters (ml) and liters (L) to measure capacity and volume. 1000 ml = 1
L. Example 1: Converting Meters to Centimeters A piece of cloth is 2.5 meters long. How long is it in centimeters?
Step 1: Remember that 1 meter = 100 centimeters.
Step 2: Multiply the length in meters by 100: 2.5 m 100 cm/m = 250 cm.
Answer: The cloth is 250 centimeters long.
Example 2: Solving a Measurement Problem A container holds 3 liters of juice. How many 250 ml glasses can be filled from the container?
Step 1: Convert liters to milliliters: 3 L 1000 ml/L = 3000 ml.
Step 2: Divide the total volume by the volume of each glass: 3000 ml / 250 ml/glass = 12 glasses.
Answer: 12 glasses can be filled. Guided Practice (With Solutions)
Question 1: A movie starts at 6:45 PM and ends at 9:05 P
M. How long is the movie?
Solution: Method: Using a timeline or subtracting times.
From 6:45 PM to 7:00 PM is 15 minutes.
From 7:00 PM to 9:00 PM is 2 hours.
From 9:00 PM to 9:05 PM is 5 minutes.
Total time: 15 minutes + 2 hours + 5 minutes = 2 hours and 20 minutes.
Answer: The movie is 2 hours and 20 minutes long.
Question 2: The temperature of water is 15°
C. It is heated and the temperature rises by 35°
C. What is the new temperature of the water?
Solution: Method: Adding the temperature change to the original temperature. 15°C + 35°C = 50°
C. Answer: The new temperature of the water is 50°
C. Question 3: A farmer has a field that is 50 meters long and 25 meters wide. What is the perimeter of the field in centimeters?
Solution: Method: First find the perimeter in meters, then convert to centimeters.