Compare Decimals
Fifth Grade Math - Complete Guide
🔄 Equivalent Decimals
What are Equivalent Decimals?
Equivalent decimals are decimal numbers that have the same value even though they look different.
Formula:
\[0.5 = 0.50 = 0.500 = \frac{5}{10} = \frac{50}{100} = \frac{500}{1000}\]
Key Rule: Trailing Zeros
âś… Adding zeros to the RIGHT does NOT change the value
\(0.3 = 0.30 = 0.300\) (All Equal)
\(2.4 = 2.40 = 2.400\) (All Equal)
❌ Adding zeros to the LEFT changes the value
\(0.3 \neq 0.03\) (NOT Equal)
\(0.3 = \frac{3}{10}\) but \(0.03 = \frac{3}{100}\)
đź’ˇ Examples
Example 1: Are \(0.6\) and \(0.60\) equivalent?
Method 1: Convert to fractions
\(0.6 = \frac{6}{10}\) and \(0.60 = \frac{60}{100} = \frac{6}{10}\)
âś“ Yes! They are equivalent because they have the same value.
Example 2: Write three equivalent decimals for \(1.2\)
Add zeros to the right: \(1.20\), \(1.200\), \(1.2000\)
âś“ Answer: \(1.2 = 1.20 = 1.200 = 1.2000\)
⚖️ Comparing Decimals
What Does It Mean?
Comparing decimals means finding which decimal is greater (\(>\)), smaller (\(<\)), or equal (\(=\)) to another decimal.
📝 Steps to Compare Decimals
- Line up the decimal points vertically
- Add trailing zeros to make the same number of decimal places
- Compare whole number parts first (left of decimal point)
- If whole numbers are equal, compare tenths place
- If tenths are equal, compare hundredths place
- Continue until you find different digits
đź’ˇ Examples
Example 1: Compare \(5.7\) and \(5.68\)
Step 1: Line up decimal points → 5.7 and 5.68
Step 2: Add trailing zeros → 5.70 and 5.68
Step 3: Compare whole numbers → 5 = 5 (equal)
Step 4: Compare tenths → 7 = 7 (equal)
Step 5: Compare hundredths → \(0 < 8\)
âś“ Answer: \(5.68 < 5.7\) or \(5.7 > 5.68\)
Example 2: Compare \(12.45\) and \(8.99\)
Step 1: Compare whole numbers → \(12 > 8\)
Step 2: We can stop here! The whole number is greater.
âś“ Answer: \(12.45 > 8.99\)
Example 3: Compare \(0.325\) and \(0.32\)
Step 1: Add trailing zeros → 0.325 and 0.320
Step 2: Compare ones → 0 = 0 (equal)
Step 3: Compare tenths → 3 = 3 (equal)
Step 4: Compare hundredths → 2 = 2 (equal)
Step 5: Compare thousandths → \(5 > 0\)
âś“ Answer: \(0.325 > 0.32\)
📊 Using Place Value Chart
How to Use the Chart
A place value chart helps us compare decimals by aligning each digit in its proper place.
Tens | Ones | â—Ź | Tenths | Hundredths | Thousandths |
---|---|---|---|---|---|
2 | 4 | . | 5 | 6 | 7 |
2 | 4 | . | 5 | 8 | 2 |
Comparing: Tens (2=2) ✓ → Ones (4=4) ✓ → Tenths (5=5) ✓ → Hundredths (6<8) ✗
Result: \(24.567 < 24.582\)
📏 Comparing Decimals on Number Lines
Number Line Rule
📌 Basic Rule:
• Numbers to the RIGHT are GREATER
• Numbers to the LEFT are SMALLER
Example: Compare \(2.3\) and \(2.7\)
2.0────2.1────2.2────2.3────2.4────2.5────2.6────2.7────2.8────2.9────3.0
↑ 2.3 is here 2.7 is here ↑
Since 2.7 is to the RIGHT of 2.3 → \(2.7 > 2.3\)
📝 Steps to Compare on Number Line
- Identify the whole number range (between which two whole numbers)
- Mark the tenths between those whole numbers
- Locate both decimal numbers on the number line
- The number on the right is greater
đź“‹ Ordering Decimals
Two Ways to Order
Ascending Order (Least to Greatest):
Arrange from smallest to largest
Example: \(0.2 < 0.5 < 0.8 < 1.1\)
Descending Order (Greatest to Least):
Arrange from largest to smallest
Example: \(5.7 > 4.2 > 3.8 > 1.1\)
📝 Steps to Order Decimals
- Write all decimals in a place value chart
- Add trailing zeros to make equal decimal places
- Compare decimals using the comparison rules
- Arrange in ascending or descending order as required
đź’ˇ Examples
Example 1: Order in ascending order: \(3.8\), \(3.08\), \(3.80\), \(0.38\)
Step 1: Add trailing zeros → 3.80, 3.08, 3.80, 0.38
Step 2: Compare whole numbers first:
• \(0 < 3\), so 0.38 is smallest
• For the three 3's, compare tenths: 0, 8, 8
• 3.08 has 0 in tenths (smallest among 3's)
• 3.8 = 3.80 (equivalent decimals)
âś“ Answer: \(0.38 < 3.08 < 3.8 = 3.80\)
Example 2: Order in descending order: \(1.25\), \(1.52\), \(1.2\), \(1.5\)
Step 1: Add trailing zeros → 1.25, 1.52, 1.20, 1.50
Step 2: All whole numbers are 1 (equal)
Step 3: Compare tenths: 2, 5, 2, 5
• 5 > 2, so decimals with 5 in tenths are larger
Step 4: For 1.52 and 1.50: compare hundredths → \(2 > 0\)
Step 5: For 1.25 and 1.20: compare hundredths → \(5 > 0\)
âś“ Answer: \(1.52 > 1.5 > 1.25 > 1.2\)
⬜ Comparing Decimals Using Grids
How Grids Work
A grid (usually 10Ă—10 = 100 squares) helps us visualize decimal values. Each square represents one hundredth (\(\frac{1}{100} = 0.01\)).
Grid Values:
• 1 column (10 squares) = \(\frac{10}{100} = 0.1\) (one tenth)
• 1 row (10 squares) = \(\frac{10}{100} = 0.1\) (one tenth)
• 1 square = \(\frac{1}{100} = 0.01\) (one hundredth)
• Whole grid (100 squares) = \(\frac{100}{100} = 1.0\) (one whole)
Comparison Rule:
The decimal with more shaded squares is greater.
đź’ˇ Example
Compare \(0.35\) and \(0.53\) using grids
Grid 1: Shade 35 squares for 0.35
Grid 2: Shade 53 squares for 0.53
Comparison: Grid 2 has more shaded squares (53 > 35)
âś“ Answer: \(0.53 > 0.35\)
đź“– Word Problems: Compare, Order, and Round
🎯 Steps to Solve Word Problems
- READ the problem carefully
- IDENTIFY the decimal numbers
- DETERMINE what the question asks (compare, order, or round)
- APPLY the correct method
- CHECK if your answer makes sense
Problem 1: Comparing
Sarah ran 3.45 kilometers and Tom ran 3.5 kilometers. Who ran farther?
Step 1: Identify decimals → 3.45 and 3.5
Step 2: Add trailing zeros → 3.45 and 3.50
Step 3: Compare: Ones (3=3) âś“, Tenths (4<5) âś—
Step 4: Since \(3.45 < 3.50\), Tom ran farther
âś“ Answer: Tom ran farther (3.5 km > 3.45 km)
Problem 2: Ordering
Four students measured their heights: Alex = 1.42 m, Ben = 1.4 m, Clara = 1.38 m, Diana = 1.45 m. Arrange them from shortest to tallest.
Step 1: Add trailing zeros → 1.42, 1.40, 1.38, 1.45
Step 2: All ones are equal (1=1=1=1)
Step 3: Compare tenths: 4, 4, 3, 4
• Clara (1.38) is shortest (3 in tenths)
Step 4: For the three with 4 in tenths, compare hundredths: 2, 0, 5
• Ben (1.40) < Alex (1.42) < Diana (1.45)
âś“ Answer: Clara (1.38 m), Ben (1.4 m), Alex (1.42 m), Diana (1.45 m)
Problem 3: Compare and Round
A book costs $12.85 and a pen costs $12.78. Which is more expensive? Round both prices to the nearest dollar.
Part 1: Compare
Compare 12.85 and 12.78:
Ones (12=12) âś“, Tenths (8=8) âś“, Hundredths (5>8) âś—
\(12.85 > 12.78\) → Book is more expensive
Part 2: Round
Round 12.85: Look at tenths (8 ≥ 5) → Round UP → $13
Round 12.78: Look at tenths (7 ≥ 5) → Round UP → $13
âś“ Answer: Book is more expensive. Both round to $13.
đź“‹ Quick Reference Guide
Concept | Key Rule | Example |
---|---|---|
Equivalent Decimals | Add zeros to the right | \(0.5 = 0.50 = 0.500\) |
Compare Decimals | Compare place by place (left to right) | \(5.67 > 5.62\) |
Number Line | Right side is greater | 3.7 is right of 3.2 |
Ascending Order | Smallest to largest | \(1.2 < 2.5 < 3.8\) |
Descending Order | Largest to smallest | \(9.1 > 6.3 > 4.2\) |
âś… Remember
Always line up decimal points when comparing!
âś… Tip
Use trailing zeros to make comparison easier!
âś… Warning
More digits doesn't mean greater! \(1.1 > 1.001\)
âś… Practice
Use place value charts for clarity!