Lesson 3: Measurement of Time and Money

📘 Introduction

Time and money are two things we use every day — from knowing when to go to school to budgeting for lunch or transport. Being able to read the time correctly and calculate money accurately are essential skills in life.

In this lesson, we’ll learn how to tell time (in hours, minutes, seconds), convert between time units, calculate durations, and solve money problems involving Ghanaian currency — cedis and pesewas.

🧠 Key Concepts and Explanations

1. Units of Time

• 1 minute = 60 seconds
• 1 hour = 60 minutes
• 1 day = 24 hours
• 1 week = 7 days
• 1 year = 12 months or 365 days (or 366 in a leap year)

Important: There are two ways to read time:

• 12-hour clock: e.g., 4:00 PM (afternoon) or 9:00 AM (morning)
• 24-hour clock: e.g., 16:00 instead of 4:00 PM

2. Reading Time on a Clock

When reading a clock:

• The short hand shows the hour
• The long hand shows the minutes

3. Duration of Time

To calculate how much time has passed or will pass, subtract start time from end time.

Example: If school starts at 7:30 AM and ends at 2:30 PM, how long is the school day?

2:30 PM – 7:30 AM = 7 hours

4. Units of Money

• 1 Ghana cedi (GH₵) = 100 pesewas (Gp)
• Money can be written as:
  • GH₵3.50 → 3 Ghana cedis and 50 pesewas
  • Gp75 → 75 pesewas = GH₵0.75

5. Real-Life Applications

• Bus arrival time = 10:15 AM
• Church starts at 8:00 AM, ends at 10:30 AM → Duration = 2.5 hours
• Price of bread = GH₵4.00; you pay GH₵5.00 → Change = GH₵1.00

🔍 Step-by-Step Sample Problems

Example 1: Convert 3 hours 20 minutes into minutes only.

Example 2: A taxi leaves at 9:15 AM and arrives at 11:45 AM. How long was the trip?

11:45 – 9:15 = 2 hours 30 minutes

Example 3: Ama buys oranges worth GH₵8.75. She gives GH₵10.00. How much change does she receive?

GH₵10.00 − GH₵8.75 = GH₵1.25

📝 Practice Exercises

A. Time Conversion

1. Convert 2 hours 45 minutes to minutes.
2. How many hours are in 150 minutes?
3. Convert 3 days to hours.

B. Time Duration

1. Kwame enters class at 7:15 AM and closes at 1:45 PM. How long is he in school?
2. A film starts at 6:00 PM and ends at 8:30 PM. What is the duration?

C. Money Calculations

1. Convert Gp 250 into Ghana cedis.
2. You buy a pen for GH₵3.60 and a book for GH₵5.90. What is the total cost?
3. You give the seller GH₵10.00. What change should you get from the purchase above?

✅ Answers and Explanations

• 2 hours 45 mins = (2×60) + 45 = 165 minutes
• 150 mins ÷ 60 = 2 hours 30 minutes
• 3 days × 24 = 72 hours
• 1:45 PM – 7:15 AM = 6 hours 30 minutes
• 8:30 PM – 6:00 PM = 2 hours 30 minutes
• Gp 250 = GH₵2.50
• GH₵3.60 + GH₵5.90 = GH₵9.50
• GH₵10.00 − GH₵9.50 = GH₵0.50

🔁 Recap

Time is measured in seconds, minutes, and hours. Money in Ghana is measured using cedis and pesewas. You should be able to convert units, calculate durations, total money, and find change. Practice these every day by checking your watch and keeping track of spending.

🪞 Reflection Prompt

How do you use time and money every day? Can you think of one situation where knowing the time helped you and another where calculating change was important?