Basic Math

Mixed operations: fractions | Fifth Grade

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:

  1. Divide the numerator by the denominator
  2. The quotient becomes the whole number
  3. The remainder becomes the new numerator
  4. 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)

âś“ Answer: \(3\frac{2}{5}\)

Mixed Number → Improper Fraction

\[\frac{(\text{Whole} \times \text{Denominator}) + \text{Numerator}}{\text{Denominator}}\]

Steps:

  1. Multiply the whole number by the denominator
  2. Add the numerator to the product
  3. 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 \(\frac{14}{3}\)

âś“ Answer: \(\frac{14}{3}\)

âž• 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

  1. Convert mixed numbers to improper fractions
  2. Find the Least Common Multiple (LCM) if denominators are different
  3. Create equivalent fractions with the same denominator
  4. Add the numerators
  5. Simplify and convert back to mixed number if needed

đź’ˇ 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 → \(\frac{8}{2} = 4\)

âś“ 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 → \(\frac{6 + 5}{15} = \frac{11}{15}\)

âś“ Answer: \(\frac{11}{15}\)

âž– 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

  1. Convert mixed numbers to improper fractions
  2. Find the LCM if denominators are different
  3. Create equivalent fractions with the same denominator
  4. Subtract the numerators
  5. Simplify and convert back to mixed number if needed

đź’ˇ 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 → \(1\frac{1}{3}\)

âś“ 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 → \(\frac{27 - 8}{36} = \frac{19}{36}\)

âś“ 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

  1. Convert mixed numbers to improper fractions
  2. Multiply the numerators together
  3. Multiply the denominators together
  4. Simplify and convert to mixed number if needed

⚠️ Important: You do NOT need a common denominator to multiply fractions!

đź’ˇ 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 → \(7\frac{17}{25}\)

âś“ 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 → \(\frac{1}{10}\)

âś“ Answer: \(\frac{1}{10}\)

âž— 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

  1. Convert mixed numbers to improper fractions
  2. KEEP the first fraction as it is
  3. CHANGE division (Ă·) to multiplication (Ă—)
  4. FLIP the second fraction (find its reciprocal)
  5. Multiply and simplify

⚠️ Remember: Reciprocal means flip the fraction! \(\frac{3}{4}\) becomes \(\frac{4}{3}\)

đź’ˇ 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 → \(\frac{6}{19}\)

âś“ 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 → \(\frac{1}{3}\)

âś“ Answer: \(\frac{1}{3}\)

đź“‹ Quick Reference: All Operations

OperationFormulaKey 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

đź“– Word Problems with Fractions & Mixed Numbers

🎯 Steps to Solve Word Problems

  1. READ the problem carefully and identify key information
  2. DETERMINE which operation to use (add, subtract, multiply, or divide)
  3. WRITE an equation to represent the problem
  4. SOLVE using the correct steps for that operation
  5. 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 → \(6\frac{3}{6} = 6\frac{1}{2}\)

âś“ 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 → \(2\frac{3}{8}\)

âś“ 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 → \(\frac{10}{6} = \frac{5}{3} = 1\frac{2}{3}\)

âś“ 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 → \(\frac{11 \times 5}{1 \times 1} = \frac{55}{1} = 55\)

âś“ Answer: 55 seeds can be planted

🔢 Multi-Step Word Problems

🎯 Strategy for Multi-Step Problems

  1. IDENTIFY all the steps needed to solve the problem
  2. BREAK DOWN the problem into smaller parts
  3. SOLVE each part in the correct order
  4. USE the result from one step in the next step
  5. CHECK your final answer makes sense

đź’ˇ 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

âś“ 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

âś“ 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

âś“ Answer: Maria can make 19 complete strips

đź’ˇ Important Tips to Remember

âś… Always Convert First

Convert mixed numbers to improper fractions before performing any operation.

âś… Simplify Your Answer

Always simplify fractions and convert improper fractions back to mixed numbers.

âś… Addition & Subtraction

Need common denominators. Find the LCM first!

âś… Multiplication & Division

Do NOT need common denominators. Just convert and multiply/divide!

🎯 Remember the Order of Operations

Parentheses → Exponents → Multiplication/Division → Addition/Subtraction

Shares: