Lesson Notes By Weeks and Term v4 - SHS 2
PROPORTIONAL REASONING
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
PROPORTIONAL REASONING
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Mathematics
Class: SHS 2
Term: 1st Term
Week: 8
Grade code: 2.1.2.LI.2
Strand code: 1
Sub-strand code: 2
Content standard code: 2.1.2.CS.2
Indicator code: 2.1.2.LI.2
Theme: NUMBERS FOR EVERYDAY LIFE
Subtheme: PROPORTIONAL REASONING
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
This lesson explores the practical application of proportional reasoning through the lens of currency exchange rates. In our interconnected world, understanding how the value of the Ghana Cedi (GHS) relates to other currencies like the US Dollar (USD), British Pound (GBP), or Nigerian Naira (NGN) is a vital life skill. It affects the price of imported goods we buy (like phones and rice), the value of money our relatives send from abroad, the cost of online shopping, and even our national economy. By mastering the concepts in this lesson, you will be empowered to make informed financial decisions.
A. Foundational Concepts: Ratio, Rate, and Proportion Ratio: A ratio compares two quantities of the *same* kind. It has no units. For example, if there are 15 boys and 20 girls in a class, the ratio of boys to girls is 15:20, which simplifies to 3:4. Rate: A rate compares two quantities of *different* kinds. It has units. For example, driving 120 km in 2 hours gives a rate of 60 km/hour. An exchange rate is a perfect example of a rate: it compares the value of one currency to another (e.g., GHS 14.50 per USD). Proportion: A proportion is a statement that two ratios or rates are equal. We use proportions to solve for unknown quantities. For example, if 2 oranges cost GHS 5.00, how much will 8 oranges cost? We set up the proportion: `(2 oranges / GHS 5.00) = (8 oranges / x)` By cross-multiplying, we find the cost. B. Understanding Exchange Rates
An exchange rate is the price of one country's currency in terms of another. These rates are not fixed; they change daily (or even hourly!) based on economic factors. You will find them at banks and Forex (Foreign Exchange) Bureaus.
When you go to a bank or forex bureau, you will see two different rates for each currency: Buying Rate: This is the rate at which the *bureau buys* the foreign currency from you. When you have dollars and you want cedis, you will be given the buying rate. This rate is always lower. Selling Rate: This is the rate at which the *bureau sells* the foreign currency to you. When you have cedis and you want to buy dollars, you will be charged the selling rate. This rate is always higher.
The difference between the buying and selling rate is how the bank or forex bureau makes its profit.