Lesson Notes By Weeks and Term v4 - JHS 1
Number and Numeration Systems
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Number and Numeration Systems
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Subject: Mathematics
Class: JHS 1
Term: 1st Term
Week: 3
Grade code: B7.1.1.1.4
Strand code: 4
Sub-strand code: 1
Content standard code: B7.1.1.1
Indicator code: B7.1.1.1.4
Theme: HANDLING DATA ...................................................................................................................................................................................................................................................................... 211
Subtheme: Number and Numeration Systems
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In our daily lives in Ghana, we often use numbers that are not whole. When we buy items at the market, the price might be GH₵ 5.75. When we listen to the news, a reporter might say the inflation rate is 19.4%. Often, we don't need the exact, long number; we need a simpler, shorter version that is "close enough." This process of simplifying numbers to a nearby value is called rounding. It helps us to estimate, communicate more easily, and make quick calculations. This lesson will teach us the important skill of rounding decimal numbers correctly.
a. Revisiting Place Value for Decimals Before we can round, we must understand the "place" of each digit in a decimal number. The decimal point separates the whole number part from the fractional part.
Let's look at the number 48.257
| Place Value | Tens | Ones | . | Tenths | Hundredths | Thousandths | | :---------- | :------: | :------: | :---: | :--------: | :------------: | :-------------: | | Digit | 4 | 8 | . | 2 | 5 | 7 | | Value | 40 | 8 | | 2/10 | 5/100 | 7/1000 | The first digit after the decimal point is in the tenths place. The second digit after the decimal point is in the hundredths place. b. The Golden Rule of Rounding Rounding is like deciding whether to climb up to the next step or stay on your current step. The decision is made by looking at the digit immediately to the right of the place you are rounding to.
The Rule: Identify your target place: Find the digit in the place you need to round to (e.g., the tenths place). Look next door: Look at the digit immediately to its right. This is your "decider" digit. Apply the 5-or-more rule: If the "decider" digit is 5, 6, 7, 8, or 9 (5 or more), you round up. This means you add 1 to your target digit. If the "decider" digit is 0, 1, 2, 3, or 4 (4 or less), you let it rest. This means your target digit stays the same. Finish up: All digits to the right of your target place become zero (or are simply dropped, in the case of decimals). c. Worked Example 1: Rounding to the Nearest Tenth Problem: A tailor measures a piece of cloth to be 2.47 metres long. Round this length to the nearest tenth of a metre.