Mixed Operations: Fractions & Mixed Numbers
Fifth Grade Math - Complete Guide
📚 What You Need to Know
Proper Fraction
A fraction where the numerator is less than the denominator.
Examples: \(\frac{3}{4}\), \(\frac{2}{5}\), \(\frac{5}{8}\)
Improper Fraction
A fraction where the numerator is greater than or equal to the denominator.
Examples: \(\frac{7}{4}\), \(\frac{9}{5}\), \(\frac{11}{3}\)
Mixed Number (Mixed Fraction)
A whole number combined with a proper fraction.
Examples: \(2\frac{1}{4}\), \(3\frac{2}{5}\), \(1\frac{7}{8}\)
🔄 Converting Between Forms
Improper Fraction → Mixed Number
\[\text{Mixed Number} = \text{Quotient} \frac{\text{Remainder}}{\text{Divisor}}\]
Steps:
- Divide the numerator by the denominator
- The quotient becomes the whole number
- The remainder becomes the new numerator
- The divisor remains as the denominator
Example: Convert \(\frac{17}{5}\) to a mixed number
Step 1: \(17 \div 5 = 3\) R 2
Step 2: Quotient = 3 (whole number)
Step 3: Remainder = 2 (new numerator)
Step 4: Divisor = 5 (denominator)
✓ Answer: \(3\frac{2}{5}\)
Mixed Number → Improper Fraction
\[\frac{(\text{Whole} \times \text{Denominator}) + \text{Numerator}}{\text{Denominator}}\]
Steps:
- Multiply the whole number by the denominator
- Add the numerator to the product
- Write the sum over the original denominator
Example: Convert \(4\frac{2}{3}\) to an improper fraction
Step 1: \(4 \times 3 = 12\)
Step 2: \(12 + 2 = 14\)
Step 3: Write as \(\frac{14}{3}\)
✓ Answer: \(\frac{14}{3}\)
➕ Addition of Fractions & Mixed Numbers
Adding Fractions (Same Denominator)
\[\frac{a}{c} + \frac{b}{c} = \frac{a + b}{c}\]
Add the numerators, keep the denominator the same!
Adding Fractions (Different Denominators)
\[\frac{a}{b} + \frac{c}{d} = \frac{ad + bc}{bd}\]
📝 Steps for Adding Mixed Numbers
- Convert mixed numbers to improper fractions
- Find the Least Common Multiple (LCM) if denominators are different
- Create equivalent fractions with the same denominator
- Add the numerators
- Simplify and convert back to mixed number if needed
💡 Examples
Example 1: \(1\frac{1}{2} + 2\frac{1}{2}\)
Step 1: Convert to improper fractions → \(\frac{3}{2} + \frac{5}{2}\)
Step 2: Denominators are the same, add numerators → \(\frac{3 + 5}{2} = \frac{8}{2}\)
Step 3: Simplify → \(\frac{8}{2} = 4\)
✓ Answer: 4
Example 2: \(\frac{2}{5} + \frac{1}{3}\)
Step 1: Find LCM of 5 and 3 → LCM = 15
Step 2: Convert to equivalent fractions → \(\frac{6}{15} + \frac{5}{15}\)
Step 3: Add numerators → \(\frac{6 + 5}{15} = \frac{11}{15}\)
✓ Answer: \(\frac{11}{15}\)
➖ Subtraction of Fractions & Mixed Numbers
Subtracting Fractions (Same Denominator)
\[\frac{a}{c} - \frac{b}{c} = \frac{a - b}{c}\]
Subtract the numerators, keep the denominator the same!
Subtracting Fractions (Different Denominators)
\[\frac{a}{b} - \frac{c}{d} = \frac{ad - bc}{bd}\]
📝 Steps for Subtracting Mixed Numbers
- Convert mixed numbers to improper fractions
- Find the LCM if denominators are different
- Create equivalent fractions with the same denominator
- Subtract the numerators
- Simplify and convert back to mixed number if needed
💡 Examples
Example 1: \(3\frac{2}{3} - 2\frac{1}{3}\)
Step 1: Convert to improper fractions → \(\frac{11}{3} - \frac{7}{3}\)
Step 2: Denominators are the same, subtract numerators → \(\frac{11 - 7}{3} = \frac{4}{3}\)
Step 3: Convert back to mixed number → \(1\frac{1}{3}\)
✓ Answer: \(1\frac{1}{3}\)
Example 2: \(\frac{3}{4} - \frac{2}{9}\)
Step 1: Find LCM of 4 and 9 → LCM = 36
Step 2: Convert to equivalent fractions → \(\frac{27}{36} - \frac{8}{36}\)
Step 3: Subtract numerators → \(\frac{27 - 8}{36} = \frac{19}{36}\)
✓ Answer: \(\frac{19}{36}\)
✖️ Multiplication of Fractions & Mixed Numbers
Multiplying Fractions Formula
\[\frac{a}{b} \times \frac{c}{d} = \frac{a \times c}{b \times d}\]
Multiply numerators together, multiply denominators together!
📝 Steps for Multiplying Mixed Numbers
- Convert mixed numbers to improper fractions
- Multiply the numerators together
- Multiply the denominators together
- Simplify and convert to mixed number if needed
⚠️ Important: You do NOT need a common denominator to multiply fractions!
💡 Examples
Example 1: \(2\frac{2}{5} \times 3\frac{1}{5}\)
Step 1: Convert to improper fractions → \(\frac{12}{5} \times \frac{16}{5}\)
Step 2: Multiply numerators → \(12 \times 16 = 192\)
Step 3: Multiply denominators → \(5 \times 5 = 25\)
Step 4: Result → \(\frac{192}{25}\)
Step 5: Convert to mixed number → \(7\frac{17}{25}\)
✓ Answer: \(7\frac{17}{25}\)
Example 2: \(\frac{1}{4} \times \frac{2}{5}\)
Step 1: Multiply numerators → \(1 \times 2 = 2\)
Step 2: Multiply denominators → \(4 \times 5 = 20\)
Step 3: Result → \(\frac{2}{20}\)
Step 4: Simplify → \(\frac{1}{10}\)
✓ Answer: \(\frac{1}{10}\)
➗ Division of Fractions & Mixed Numbers
Dividing Fractions Formula
\[\frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c}\]
Keep → Change → Flip (Multiply by the reciprocal)
📝 Steps for Dividing Mixed Numbers
- Convert mixed numbers to improper fractions
- KEEP the first fraction as it is
- CHANGE division (÷) to multiplication (×)
- FLIP the second fraction (find its reciprocal)
- Multiply and simplify
⚠️ Remember: Reciprocal means flip the fraction! \(\frac{3}{4}\) becomes \(\frac{4}{3}\)
💡 Examples
Example 1: \(1\frac{1}{5} \div 3\frac{4}{5}\)
Step 1: Convert to improper fractions → \(\frac{6}{5} \div \frac{19}{5}\)
Step 2: Keep first fraction → \(\frac{6}{5}\)
Step 3: Change ÷ to × → \(\frac{6}{5} \times\)
Step 4: Flip second fraction → \(\frac{6}{5} \times \frac{5}{19}\)
Step 5: Multiply → \(\frac{6 \times 5}{5 \times 19} = \frac{30}{95}\)
Step 6: Simplify → \(\frac{6}{19}\)
✓ Answer: \(\frac{6}{19}\)
Example 2: \(\frac{1}{12} \div \frac{1}{4}\)
Step 1: Keep → \(\frac{1}{12}\)
Step 2: Change → \(\frac{1}{12} \times\)
Step 3: Flip → \(\frac{1}{12} \times \frac{4}{1}\)
Step 4: Multiply → \(\frac{1 \times 4}{12 \times 1} = \frac{4}{12}\)
Step 5: Simplify → \(\frac{1}{3}\)
✓ Answer: \(\frac{1}{3}\)
📋 Quick Reference: All Operations
| Operation | Formula | Key Rule |
|---|---|---|
| Addition | \(\frac{a}{b} + \frac{c}{d} = \frac{ad + bc}{bd}\) | Need common denominators |
| Subtraction | \(\frac{a}{b} - \frac{c}{d} = \frac{ad - bc}{bd}\) | Need common denominators |
| Multiplication | \(\frac{a}{b} \times \frac{c}{d} = \frac{ac}{bd}\) | NO common denominator needed |
| Division | \(\frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c}\) | Keep-Change-Flip |
📖 Word Problems with Fractions & Mixed Numbers
🎯 Steps to Solve Word Problems
- READ the problem carefully and identify key information
- DETERMINE which operation to use (add, subtract, multiply, or divide)
- WRITE an equation to represent the problem
- SOLVE using the correct steps for that operation
- CHECK if the answer makes sense
Problem 1: Addition Word Problem
There are \(2\frac{1}{3}\) pounds of red apples and \(4\frac{1}{6}\) pounds of green apples. How many pounds of apples are there in all?
Step 1: Write equation → \(2\frac{1}{3} + 4\frac{1}{6}\)
Step 2: Convert to improper fractions → \(\frac{7}{3} + \frac{25}{6}\)
Step 3: Find LCM (6) and create equivalent fractions → \(\frac{14}{6} + \frac{25}{6}\)
Step 4: Add → \(\frac{14 + 25}{6} = \frac{39}{6}\)
Step 5: Convert to mixed number and simplify → \(6\frac{3}{6} = 6\frac{1}{2}\)
✓ Answer: \(6\frac{1}{2}\) pounds of apples
Problem 2: Subtraction Word Problem
A recipe calls for \(3\frac{1}{4}\) cups of strawberries. If Tyler has \(5\frac{5}{8}\) cups of strawberries, how many will he have left after he makes 1 recipe?
Step 1: Write equation → \(5\frac{5}{8} - 3\frac{1}{4}\)
Step 2: Convert to improper fractions → \(\frac{45}{8} - \frac{13}{4}\)
Step 3: Find LCM (8) and create equivalent fractions → \(\frac{45}{8} - \frac{26}{8}\)
Step 4: Subtract → \(\frac{45 - 26}{8} = \frac{19}{8}\)
Step 5: Convert to mixed number → \(2\frac{3}{8}\)
✓ Answer: \(2\frac{3}{8}\) cups left
Problem 3: Multiplication Word Problem
A recipe requires \(\frac{2}{3}\) cup of flour. If you want to make \(2\frac{1}{2}\) batches, how much flour do you need?
Step 1: Write equation → \(\frac{2}{3} \times 2\frac{1}{2}\)
Step 2: Convert to improper fractions → \(\frac{2}{3} \times \frac{5}{2}\)
Step 3: Multiply numerators → \(2 \times 5 = 10\)
Step 4: Multiply denominators → \(3 \times 2 = 6\)
Step 5: Simplify → \(\frac{10}{6} = \frac{5}{3} = 1\frac{2}{3}\)
✓ Answer: \(1\frac{2}{3}\) cups of flour
Problem 4: Division Word Problem
Each seed needs \(\frac{1}{5}\) cup of soil. How many seeds can be planted with 11 cups of soil?
Step 1: Write equation → \(11 \div \frac{1}{5}\)
Step 2: Convert 11 to fraction → \(\frac{11}{1} \div \frac{1}{5}\)
Step 3: Keep-Change-Flip → \(\frac{11}{1} \times \frac{5}{1}\)
Step 4: Multiply → \(\frac{11 \times 5}{1 \times 1} = \frac{55}{1} = 55\)
✓ Answer: 55 seeds can be planted
🔢 Multi-Step Word Problems
🎯 Strategy for Multi-Step Problems
- IDENTIFY all the steps needed to solve the problem
- BREAK DOWN the problem into smaller parts
- SOLVE each part in the correct order
- USE the result from one step in the next step
- CHECK your final answer makes sense
💡 Tip: Follow the order of operations (PEMDAS) when solving!
Multi-Step Problem 1
Sarah bought \(2\frac{1}{2}\) pounds of apples and \(1\frac{3}{4}\) pounds of oranges. She used \(\frac{2}{3}\) of the total fruit to make a fruit salad. How many pounds of fruit did she use?
Step 1: Find total fruit → \(2\frac{1}{2} + 1\frac{3}{4}\)
Convert: \(\frac{5}{2} + \frac{7}{4} = \frac{10}{4} + \frac{7}{4} = \frac{17}{4} = 4\frac{1}{4}\) pounds
Step 2: Find \(\frac{2}{3}\) of total → \(4\frac{1}{4} \times \frac{2}{3}\)
Convert: \(\frac{17}{4} \times \frac{2}{3} = \frac{34}{12} = \frac{17}{6} = 2\frac{5}{6}\) pounds
✓ Answer: Sarah used \(2\frac{5}{6}\) pounds of fruit
Multi-Step Problem 2
A ribbon is \(12\frac{1}{2}\) feet long. Alex cuts off \(3\frac{1}{4}\) feet and then divides the remaining ribbon into 4 equal pieces. How long is each piece?
Step 1: Find remaining ribbon → \(12\frac{1}{2} - 3\frac{1}{4}\)
Convert: \(\frac{25}{2} - \frac{13}{4} = \frac{50}{4} - \frac{13}{4} = \frac{37}{4} = 9\frac{1}{4}\) feet
Step 2: Divide into 4 pieces → \(9\frac{1}{4} \div 4\)
Convert: \(\frac{37}{4} \div \frac{4}{1} = \frac{37}{4} \times \frac{1}{4} = \frac{37}{16} = 2\frac{5}{16}\) feet
✓ Answer: Each piece is \(2\frac{5}{16}\) feet long
Multi-Step Problem 3
Maria had \(8\frac{3}{4}\) yards of fabric. She used \(2\frac{1}{3}\) yards to make a dress and \(1\frac{1}{2}\) yards to make a shirt. She then cut the remaining fabric into strips that are each \(\frac{1}{4}\) yard long. How many strips can she make?
Step 1: Find fabric used → \(2\frac{1}{3} + 1\frac{1}{2}\)
Convert: \(\frac{7}{3} + \frac{3}{2} = \frac{14}{6} + \frac{9}{6} = \frac{23}{6}\) yards
Step 2: Find remaining fabric → \(8\frac{3}{4} - \frac{23}{6}\)
Convert: \(\frac{35}{4} - \frac{23}{6} = \frac{105}{12} - \frac{46}{12} = \frac{59}{12}\) yards
Step 3: Divide into \(\frac{1}{4}\) yard strips → \(\frac{59}{12} \div \frac{1}{4}\)
Keep-Change-Flip: \(\frac{59}{12} \times \frac{4}{1} = \frac{236}{12} = \frac{59}{3} = 19\frac{2}{3}\)
Since we can only make whole strips → 19 strips
✓ Answer: Maria can make 19 complete strips
💡 Important Tips to Remember
✅ Always Convert First
Convert mixed numbers to improper fractions before performing any operation.
✅ Simplify Your Answer
Always simplify fractions and convert improper fractions back to mixed numbers.
✅ Addition & Subtraction
Need common denominators. Find the LCM first!
✅ Multiplication & Division
Do NOT need common denominators. Just convert and multiply/divide!
🎯 Remember the Order of Operations
Parentheses → Exponents → Multiplication/Division → Addition/Subtraction
