Lesson Notes By Weeks and Term v4 - JHS 1
Number Operations
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Number Operations
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Subject: Mathematics
Class: JHS 1
Term: 1st Term
Week: 7
Grade code: B7.1.2.2.3
Strand code: 4
Sub-strand code: 2
Content standard code: B7.1.2.1
Indicator code: B7.1.2.2.3
Theme: HANDLING DATA ...................................................................................................................................................................................................................................................................... 211
Subtheme: Number Operations
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This lesson focuses on applying our knowledge of addition, subtraction, multiplication, and division to solve real-world problems involving decimal numbers. Decimals are all around us in Ghana – from the price of items at the market (like GH₵5.50), to measuring fabric (2.5 metres), to checking the weight of produce (12.8 kg). Being able to confidently solve story problems with decimals is a crucial skill for everyday life, helping us to manage money, measure accurately, and make informed decisions. We will learn how to read a problem, decide which operation to use, and calculate the correct answer.
A. Understanding Story Problems
Story problems (or word problems) describe a real-life situation using words and numbers. Our job is to translate these words into a mathematical equation and then solve it. A good strategy is the R-U-P-S-C method: R - Read: Read the entire problem carefully to understand the story. U - Underline: Underline the question being asked. What do you need to find? P - Plan: Decide which operation (+, -, ×, ÷) to use. Look for keywords. S - Solve: Perform the calculation. C - Check: Does your answer make sense? Write the answer with the correct units (e.g., kg, GH₵, m). B. Keywords for Operations
Look for these words to help you decide which operation to use: Addition (+): *total, altogether, sum, combine, and, plus, in all* Subtraction (-): *less than, difference, how much more, left, remain, take away, reduce* Multiplication (×): *times, of, product, total for multiple items, each* Division (÷): *share equally, per, average, out of, split, goes into* C. Review of Decimal Operations Addition and Subtraction of Decimals The most important rule is to line up the decimal points vertically. Add or subtract as you would with whole numbers, and then bring the decimal point straight down in your answer. Example: A seamstress buys 2.5 metres of wax print and 1.75 metres of linen. What is the total length of fabric she bought? Keyword: "total" means addition. Setup: ``` 2.50 (add a zero as a placeholder) + 1.75 ------ ``` Solution: ``` 2.50 + 1.75 ------ 4.25 ``` Answer: She bought a total of 4.25 metres of fabric. Multiplication of Decimals Multiply the numbers as if they were whole numbers (ignore the decimal points initially). Then, count the total number of decimal places in the numbers you multiplied. Place the decimal point in your answer so it has that same number of decimal places. Example: Esi buys 3 notebooks, and each notebook costs GH₵8.50. How much does she pay in total? Keyword: "each" suggests multiplication for a total. Setup: 8.50 × 3 Solution: Multiply without decimals: 850 × 3 = 2550 Count decimal places: 8.50 has two decimal places. 3 has zero. Total = 2. Place the decimal point two places from the right in the answer: 25.50 Answer: Esi pays GH₵25.50. Division of Decimals The key is to make the divisor (the number you are dividing by) a whole number. Example: A farmer harvests 34.5 kg of cassava from 3 plants. If each plant gave the same amount, what is the average weight of cassava per plant? Keyword: "average" or "per plant" means division. Setup: 34.5 ÷ 3 Solution: The divisor (3) is already a whole number. So, we divide as usual and place the decimal point in the answer directly above the decimal point in the dividend. ``` 11.5 _______ 3 | 34.5 -3 --- 04 3 --- 1 5 1 5 ----- 0 ``` Answer: The average weight is 11.5 kg per plant.
Guided Practice (With Solutions)