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Number - Comparing and Ordering Numbers

Grade 3IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Place Value Columns: To compare numbers, we look at the value of each digit based on its position. Imagine a grid with columns for Thousands (ThTh), Hundreds (HH), Tens (TT), and Ones (OO). When comparing two numbers like 4,5324,532 and 4,5194,519, we line them up in these columns to see which digits are different.

The Alligator Rule (Comparison Symbols): We use special symbols to show which number is bigger. The 'Greater Than' symbol (>>) and the 'Less Than' symbol (<<) look like an open alligator's mouth. The 'mouth' always opens toward the larger number. The 'Equal To' symbol (==) is used when both numbers have the exact same value.

Left-to-Right Comparison: Always start comparing from the largest place value (the digit furthest to the left). For example, in the numbers 3,4503,450 and 2,9992,999, we look at the Thousands place first. Since 3,000>2,0003,000 > 2,000, we know 3,4503,450 is greater without even looking at the other digits.

Counting Digits: A quick way to compare is to count how many digits a number has. A number with more digits is always greater than a number with fewer digits. For example, 1,0001,000 (4 digits) is always larger than 999999 (3 digits). Visualise this as a tall stack of blocks versus a shorter stack.

Ascending Order: This means arranging numbers from the smallest value to the largest value. Think of this like climbing up a staircase, where the first step is the lowest number (e.g., 10203010 \rightarrow 20 \rightarrow 30).

Descending Order: This means arranging numbers from the largest value to the smallest value. Think of this like walking down a slide or a staircase, starting from the top with the biggest number (e.g., 500400300500 \rightarrow 400 \rightarrow 300).

The Number Line: Numbers can be placed on a horizontal line with arrows at both ends. On a number line, values increase as you move to the right and decrease as you move to the left. If number AA is to the right of number BB, then A>BA > B.

Tie-Breaking: If the digits in the highest place value are the same, move one column to the right and compare those digits. Continue this process until you find digits that are different. For example, to compare 6,7826,782 and 6,7916,791, both have 66 thousands and 77 hundreds, so we compare the tens: 88 tens is less than 99 tens.

📐Formulae

a>ba > b (a is greater than b)

a<ba < b (a is less than b)

a=ba = b (a is equal to b)

Place Value Representation: (1,000×Th)+(100×H)+(10×T)+(1×O)(1,000 \times Th) + (100 \times H) + (10 \times T) + (1 \times O)

💡Examples

Problem 1:

Compare the numbers 5,6725,672 and 5,6815,681 using the correct symbol (>>, <<, or ==).

Solution:

Step 1: Compare the thousands place. Both have 55 (5,000=5,0005,000 = 5,000). Step 2: Compare the hundreds place. Both have 66 (600=600600 = 600). Step 3: Compare the tens place. The first number has 77 (7070) and the second has 88 (8080). Since 7<87 < 8, then 5,672<5,6815,672 < 5,681.

Explanation:

We compare digits from left to right. Since the thousands and hundreds were identical, the tens place determined which number was larger.

Problem 2:

Arrange the following numbers in ascending order: 4,2034,203, 456456, 4,2304,230.

Solution:

Step 1: Count the digits. 456456 has 3 digits, while the others have 4. So, 456456 is the smallest. Step 2: Compare 4,2034,203 and 4,2304,230. Both have 44 in the thousands and 22 in the hundreds. Step 3: Compare the tens. 0<30 < 3, so 4,203<4,2304,203 < 4,230. The final order is 456,4,203,4,230456, 4,203, 4,230.

Explanation:

Ascending order means smallest to largest. We first identified the number with the fewest digits, then compared the remaining numbers using place value.