\(\displaystyle {\left(-\frac{15}{8}\right) \times \left(-\frac{6}{5}\right)}\)
Cancel 15 & 5 (3, 1); 6 & 8 (3, 4)
\(= \frac{3 \times 3}{4 \times 1} = \mathbf{\frac{9}{4}}\text{ or }\mathbf{2\frac{1}{4}}\)
\(\displaystyle {\left(-\frac{10}{3}\right) \times \frac{21}{20}}\)
Cancel 10 & 20 (1, 2); 3 & 21 (1, 7)
\(= -\frac{1 \times 7}{1 \times 2} = \mathbf{-\frac{7}{2}}\text{ or }\mathbf{-3\frac{1}{2}}\)
Answers
\(-\frac{1}{4}\)
\(-\frac{1}{4}\)
\(\frac{1}{6}\)
\(\frac{1}{9}\)
\(-\frac{1}{6}\)
\(-\frac{1}{6}\)
\(\frac{1}{12}\)
\(-\frac{4}{35}\)
\(-\frac{3}{4}\)
\(-\frac{3}{2}\) / \(-1\frac{1}{2}\)
\(\frac{9}{4}\) / \(2\frac{1}{4}\)
\(-\frac{7}{2}\) / \(-3\frac{1}{2}\)
Pair 2: 10 & 25 GCF:
Factor pairs (10):
Factor pairs (25):
Pair 1: 6 & 8 GCF:
Factor pairs (6):
Factor pairs (8):
Pair 2: 5 & 5 GCF:
Factor pairs (5):
Factor pairs (5):
Pair 1: 8 & 16 GCF:
Factor pairs (8):
Factor pairs (16):
Pair 2: 9 & 3 GCF:
Factor pairs (9):
Factor pairs (3):
Pair 1: 15 & 5 GCF:
Factor pairs (15):
Factor pairs (5):
Pair 2: 6 & 8 GCF:
Factor pairs (6):
Factor pairs (8):
Pair 1: 10 & 20 GCF:
Factor pairs (10):
Factor pairs (20):
Pair 2: 21 & 3 GCF:
Factor pairs (21):
Factor pairs (3):
* For mixed numbers (9–12), convert to improper fractions first to reveal the diagonal numerator and denominator pairs. Factor Pairs Organizer
\(\displaystyle {-\frac{5}{2} \times \frac{10}{7}}\)
Cancel 2 & 10 by 2 (1, 5) \(\rightarrow \mathbf{-\frac{25}{7}\text{ or }-3\frac{4}{7}}\)
\(\displaystyle {\frac{10}{3} \times \left(-\frac{13}{4}\right)}\)
Cancel 10 & 4 by 2 (5, 2) \(\rightarrow \mathbf{-\frac{65}{6}\text{ or }-10\frac{5}{6}}\)
\(\displaystyle {-\frac{17}{8} \times \left(-\frac{20}{7}\right)}\)
Cancel 8 & 20 by 4 (2, 5) \(\rightarrow \mathbf{\frac{85}{14}\text{ or }6\frac{1}{14}}\)
\(\displaystyle {-\frac{11}{8} \times \frac{12}{7}}\)
Cancel 8 & 12 by 4 (2, 3) \(\rightarrow \mathbf{-\frac{33}{14}\text{ or }-2\frac{5}{14}}\)
\(\displaystyle {\frac{7}{8} \times \left(-\frac{10}{7}\right)}\)
Cancel 7 & 7 (1, 1); 8 & 10 (4, 5) \(\rightarrow \mathbf{-\frac{5}{4}\text{ or }-1\frac{1}{4}}\)
\(\displaystyle {-\frac{10}{9} \times \left(-\frac{5}{4}\right)}\)
Cancel 10 & 4 by 2 (5, 2) \(\rightarrow \mathbf{\frac{25}{18}\text{ or }1\frac{7}{18}}\)
Answers
\(-\frac{2}{15}\)
\(-\frac{1}{3}\)
\(\frac{1}{5}\)
\(\frac{7}{10}\)
\(-\frac{1}{14}\)
\(-\frac{1}{4}\)
\(\frac{1}{3}\)
\(-\frac{1}{3}\)
\(\frac{1}{2}\)
\(\frac{1}{48}\)
\(-\frac{1}{63}\)
\(-\frac{1}{30}\)
\(-\frac{25}{7}\) / \(-3\frac{4}{7}\)
\(-\frac{65}{6}\) / \(-10\frac{5}{6}\)
\(\frac{85}{14}\) / \(6\frac{1}{14}\)
\(-\frac{33}{14}\) / \(-2\frac{5}{14}\)
\(-\frac{5}{4}\) / \(-1\frac{1}{4}\)
\(\frac{25}{18}\) / \(1\frac{7}{18}\)
Answers
\(-\frac{3}{2}\)
* Use model problem #2 as your guide to convert mixed numbers, find diagonal factor pairs, and cross-cancel. 6-Problem Practice Sheet
Fraction Multiplication Quiz (Questions 6–10)
Name: Questions 9 & 10 contain mixed numbers
Q6 \(\displaystyle {-\frac{6}{25} \times \frac{15}{16} =}\)
Answer:
Diagonal 1: (6 & 16) GCF:
Factors of 6:
Factors of 16:
Cross-reduce? [ ] Yes [ ] No
Diagonal 2: (15 & 25) GCF:
Factors of 15:
Factors of 25:
Cross-reduce? [ ] Yes [ ] No
Cross-Cancel & Show Work:
Q7 \(\displaystyle {-\frac{14}{15} \times \left(-\frac{5}{21}\right) =}\)
Answer:
Diagonal 1: (14 & 21) GCF:
Factors of 14:
Factors of 21:
Cross-reduce? [ ] Yes [ ] No
Diagonal 2: (5 & 15) GCF:
Factors of 5:
Factors of 15:
Cross-reduce? [ ] Yes [ ] No
Cross-Cancel & Show Work:
Q8 \(\displaystyle {\frac{7}{10} \times \frac{5}{11} =}\)
Answer:
Diagonal 1: (7 & 11) GCF:
Factors of 7:
Factors of 11:
Cross-reduce? [ ] Yes [ ] No
Diagonal 2: (5 & 10) GCF:
Factors of 5:
Factors of 10:
Cross-reduce? [ ] Yes [ ] No
Cross-Cancel & Show Work:
Q9 \(\displaystyle {-1\frac{1}{5} \times \frac{5}{9} =}\) Improper:
Answer:
Diagonal 1: (6 & 9) GCF:
Factors of 6:
Factors of 9:
Cross-reduce? [ ] Yes [ ] No
Diagonal 2: (5 & 5) GCF:
Factors of 5:
Factors of 5:
Cross-reduce? [ ] Yes [ ] No
Cross-Cancel & Show Work:
Q10 \(\displaystyle {1\frac{7}{8} \times \left(-1\frac{1}{5}\right) =}\) Improper:
Answer:
Diagonal 1: (15 & 5) GCF:
Factors of 15:
Factors of 5:
Cross-reduce? [ ] Yes [ ] No
Diagonal 2: (6 & 8) GCF:
Factors of 6:
Factors of 8:
Cross-reduce? [ ] Yes [ ] No
Cross-Cancel & Show Work:
* Make sure all signs (\(+\) or \(-\)) and simplest fraction forms are accurately shown. Page 2 of 3
Determine the sign of integer products, then study the mixed number transformation guide.
Name: Q11–Q15: 4 pts each
Questions 11–15: Determine whether each integer product is POSITIVE or NEGATIVE, then solve. Check exactly one box per question
Q11 \((-8) \times (-7)\)
Sign of final answer:
[ ] Positive (+) [ ] Negative (−)
Product:
Q12 \(9 \times (-6)\)
Sign of final answer:
[ ] Positive (+) [ ] Negative (−)
Product:
Q13 \((-7) \times 5\)
Sign of final answer:
[ ] Positive (+) [ ] Negative (−)
Product:
Q14 \((-6) \times (-4)\)
Sign of final answer:
[ ] Positive (+) [ ] Negative (−)
Product:
Q15 \(8 \times (-3)\)
Sign of final answer:
[ ] Positive (+) [ ] Negative (−)
Product:
Scratch Work / Notes
Solution Guide How to Solve a Mixed Number Multiplication Problem
Problem: \(\displaystyle {1\frac{2}{3} \times \left(-2\frac{1}{4}\right)}\)
Complete Mathematical Transformation: Problem → Improper → Cross-Reduced → Final Answer
1. Original Problem
\(\displaystyle {1\frac{2}{3} \times \left(-2\frac{1}{4}\right)}\)
2. Improper Fractions
\(\displaystyle {\frac{5}{3} \times \left(-\frac{9}{4}\right)}\)
3. Cross-Cancel (\(\div 3\))
\(\displaystyle {\frac{5}{\mathbf{1}} \times \left(-\frac{\mathbf{3}}{4}\right)}\)
4. Final Answer
\(\displaystyle {-\frac{15}{4} = \mathbf{-3\frac{3}{4}}}\)
1 Convert to Improper Fractions
Multiply denominator by whole number, add numerator. Keep the negative sign outside!
\(1\frac{2}{3} = \frac{(1 \times 3) + 2}{3} = \mathbf{\frac{5}{3}}\)
\(-2\frac{1}{4} = -\frac{(2 \times 4) + 1}{4} = \mathbf{-\frac{9}{4}}\)
Becomes: \(\mathbf{\frac{5}{3} \times \left(-\frac{9}{4}\right)}\)
2 Determine Product Sign
Apply Part 2 integer multiplication rules to set the correct sign upfront.
\(\text{Positive} \times \text{Negative} = \mathbf{\text{Negative}}\)
One negative factor means the final answer must have a minus sign (−).
Sign: \(\mathbf{-}\)
3 List Factor Pairs & Cross-Cancel
Check both diagonals to see if any diagonal pair shares a \(\text{GCF} > 1\).
Diagonal (9 & 3): \(\text{GCF} = 3\). Cross-reduce: \(9 \div 3 = \mathbf{3}\); \(3 \div 3 = \mathbf{1}\).
Diagonal (5 & 4): \(\text{GCF} = 1\). Cannot reduce! (Keep 5 & 4).
4 Multiply Straight Across
Multiply reduced numerators and denominators. Convert improper to mixed number.
\(\frac{5}{1} \times \left(-\frac{3}{4}\right) = -\frac{5 \times 3}{1 \times 4} = \mathbf{-\frac{15}{4}}\)
Division: \(15 \div 4 = 3\text{ R }3 \rightarrow \mathbf{-3\frac{3}{4}}\)
Becomes: \(\mathbf{-3\frac{3}{4}}\) or \(\mathbf{-\frac{15}{4}}\)
Key Rule: Convert mixed numbers to improper fractions before cross-cancelling or multiplying! Keep this reference handy
* Total Test: 10 Fraction Problems (8 pts each = 80 pts) + 5 Integer Problems (4 pts each = 20 pts) = 100 Points. Page 3 of 3
Answer: \(\mathbf{\frac{3}{10}}\)
Diagonal 1: (9 & 15) GCF: 3
9: 1 × 9, 3 × 3
15: 1 × 15, 3 × 5
Cross-reduce? [✓] Yes (\(\div 3 \rightarrow 3, 5\))
Diagonal 2: (8 & 16) GCF: 8
8: 1 × 8, 2 × 4
16: 1 × 16, 2 × 8, 4 × 4
Cross-reduce? [✓] Yes (\(\div 8 \rightarrow 1, 2\))
Cross-Cancel & Solution:
\(\frac{3}{2} \times \frac{1}{5} = \frac{3}{10}\)
* Diagnostic Check: Question 4 tests student awareness that \(\text{GCF}=1\) means no reduction occurs on that diagonal. Page 1 of 3
Fraction Multiplication Quiz Answer Key (Questions 6–10)
Mixed Number Solutions on Q9 & Q10
Q6 \(\displaystyle {-\frac{6}{25} \times \frac{15}{16} =}\)
Answer: \(\mathbf{-\frac{9}{40}}\)
Diagonal 1: (6 & 16) GCF: 2
6: 1 × 6, 2 × 3
16: 1 × 16, 2 × 8, 4 × 4
Cross-reduce? [✓] Yes (\(\div 2 \rightarrow 3, 8\))
Diagonal 2: (15 & 25) GCF: 5
15: 1 × 15, 3 × 5
25: 1 × 25, 5 × 5
Cross-reduce? [✓] Yes (\(\div 5 \rightarrow 3, 5\))
Cross-Cancel & Solution:
\(-\frac{3}{5} \times \frac{3}{8} = -\frac{9}{40}\)
Q7 \(\displaystyle {-\frac{14}{15} \times \left(-\frac{5}{21}\right) =}\)
Answer: \(\mathbf{\frac{2}{9}}\)
Diagonal 1: (14 & 21) GCF: 7
14: 1 × 14, 2 × 7
21: 1 × 21, 3 × 7
Cross-reduce? [✓] Yes (\(\div 7 \rightarrow 2, 3\))
Diagonal 2: (5 & 15) GCF: 5
5: 1 × 5
15: 1 × 15, 3 × 5
Cross-reduce? [✓] Yes (\(\div 5 \rightarrow 1, 3\))
Cross-Cancel & Solution:
\(-\frac{2}{3} \times \left(-\frac{1}{3}\right) = +\frac{2}{9}\)
Q8 \(\displaystyle {\frac{7}{10} \times \frac{5}{11} =}\)
Answer: \(\mathbf{\frac{7}{22}}\)
Diagonal 1: (7 & 11) GCF: 1
7: 1 × 7
11: 1 × 11
Cross-reduce? [✓] No (\(\text{GCF}=1\), keep 7 & 11)
Diagonal 2: (5 & 10) GCF: 5
5: 1 × 5
10: 1 × 10, 2 × 5
Cross-reduce? [✓] Yes (\(\div 5 \rightarrow 1, 2\))
Cross-Cancel & Solution:
\(\frac{7}{2} \times \frac{1}{11} = \frac{7}{22}\)
Q9 \(\displaystyle {-1\frac{1}{5} \times \frac{5}{9} =}\) Improper: \(-\frac{6}{5}\)
Answer: \(\mathbf{-\frac{2}{3}}\)
Diagonal 1: (6 & 9) GCF: 3
6: 1 × 6, 2 × 3
9: 1 × 9, 3 × 3
Cross-reduce? [✓] Yes (\(\div 3 \rightarrow 2, 3\))
Diagonal 2: (5 & 5) GCF: 5
5: 1 × 5
5: 1 × 5
Cross-reduce? [✓] Yes (\(\div 5 \rightarrow 1, 1\))
Cross-Cancel & Solution:
\(-\frac{2}{1} \times \frac{1}{3} = -\frac{2}{3}\)
Q10 \(\displaystyle {1\frac{7}{8} \times \left(-1\frac{1}{5}\right) =}\) Improper: \(\frac{15}{8} \times \left(-\frac{6}{5}\right)\)
Answer: \(\mathbf{-\frac{9}{4}}\) or \(\mathbf{-2\frac{1}{4}}\)
Diagonal 1: (15 & 5) GCF: 5
15: 1 × 15, 3 × 5
5: 1 × 5
Cross-reduce? [✓] Yes (\(\div 5 \rightarrow 3, 1\))
Diagonal 2: (6 & 8) GCF: 2
6: 1 × 6, 2 × 3
8: 1 × 8, 2 × 4
Cross-reduce? [✓] Yes (\(\div 2 \rightarrow 3, 4\))
Cross-Cancel & Solution:
\(\frac{3}{4} \times \left(-\frac{3}{1}\right) = -\frac{9}{4} = -2\frac{1}{4}\)
* Answers may be expressed as improper fractions or mixed numbers; both are mathematically equivalent. Page 2 of 3
Solutions for integer multiplication sign checks and the pedagogical worked guide.
Q11–Q15: 4 pts each
Questions 11–15 Solutions: Single-digit integer products and sign determinations. 2 pts for correct sign + 2 pts for correct value
Q11 \((-8) \times (-7)\)
Sign of final answer:
[✓] Positive (+) [ ] Negative (−)
Product: \(\mathbf{+56}\)
Q12 \(9 \times (-6)\)
Sign of final answer:
[ ] Positive (+) [✓] Negative (−)
Product: \(\mathbf{-54}\)
Q13 \((-7) \times 5\)
Sign of final answer:
[ ] Positive (+) [✓] Negative (−)
Product: \(\mathbf{-35}\)
Q14 \((-6) \times (-4)\)
Sign of final answer:
[✓] Positive (+) [ ] Negative (−)
Product: \(\mathbf{+24}\)
Q15 \(8 \times (-3)\)
Sign of final answer:
[ ] Positive (+) [✓] Negative (−)
Product: \(\mathbf{-24}\)
Scoring Guidelines (Q11–Q15):
• Sign Identification: 2 pts
• Correct Product: 2 pts
4 pts each • 20 pts total
Solution Guide Pedagogical Framework: Mixed Number Cross-Cancellation
Example: \(\displaystyle {1\frac{2}{3} \times \left(-2\frac{1}{4}\right)}\)
Complete Mathematical Transformation: Problem → Improper → Cross-Reduced → Final Answer
1. Original Problem
\(\displaystyle {1\frac{2}{3} \times \left(-2\frac{1}{4}\right)}\)
2. Improper Fractions
\(\displaystyle {\frac{5}{3} \times \left(-\frac{9}{4}\right)}\)
3. Cross-Cancel (\(\div 3\))
\(\displaystyle {\frac{5}{\mathbf{1}} \times \left(-\frac{\mathbf{3}}{4}\right)}\)
4. Final Answer
\(\displaystyle {-\frac{15}{4} = \mathbf{-3\frac{3}{4}}}\)
1 Convert to Improper Fractions
Common error: Multiplying whole numbers together. Ensure students convert mixed numbers to improper fractions before reducing.
\(1\frac{2}{3} = \frac{(1 \times 3) + 2}{3} = \mathbf{\frac{5}{3}}\)
\(-2\frac{1}{4} = -\frac{(2 \times 4) + 1}{4} = \mathbf{-\frac{9}{4}}\)
Becomes: \(\mathbf{\frac{5}{3} \times \left(-\frac{9}{4}\right)}\)
2 Determine Product Sign
Connecting Part 2 integer rules to fractions: count negative factors first to prevent sign drops in the final answer.
\(\text{Positive} \times \text{Negative} = \mathbf{\text{Negative}}\)
One negative factor means the final answer must have a minus sign (−).
Sign: \(\mathbf{-}\)
3 List Factor Pairs & Cross-Cancel
Highlighting both reducible and non-reducible diagonals so students don't force cross-cancellation where GCF = 1.
Diagonal (9 & 3): \(\text{GCF} = 3\). Cross-reduce: \(9 \div 3 = \mathbf{3}\); \(3 \div 3 = \mathbf{1}\).
Diagonal (5 & 4): \(\text{GCF} = 1\). Cannot reduce! (Keep 5 & 4).
4 Multiply Straight Across
Multiply reduced numerators and denominators. Accept either improper fraction or mixed number.
\(\frac{5}{1} \times \left(-\frac{3}{4}\right) = -\frac{5 \times 3}{1 \times 4} = \mathbf{-\frac{15}{4}}\)
Division: \(15 \div 4 = 3\text{ R }3 \rightarrow \mathbf{-3\frac{3}{4}}\)
Accepted: \(\mathbf{-3\frac{3}{4}}\) or \(\mathbf{-\frac{15}{4}}\)
Teacher Note: Emphasize that cross-cancelling keeps numbers small so students don't need large division algorithms at the end! Scoring Complete
* Total Test: 10 Fraction Problems (8 pts each = 80 pts) + 5 Integer Problems (4 pts each = 20 pts) = 100 Points. Page 3 of 3
?
3. Whole Number
\( 8 \)
Reciprocal:
?
4. Improper Fraction
\( \frac{11}{3} \)
Reciprocal:
?
Self-Check Test: Multiply your answer by the original number. If it equals 1, your reciprocal is correct!
Worked Example
Complete Problem
Problem \( \frac{4}{9} \div \frac{8}{15} \)
Evaluate & simplify fully
1 Apply KCF
Multiply by the reciprocal of \( \frac{8}{15} \):
\( \frac{4}{9} \times \frac{15}{8} \)
2 Cross Cancel!
Reduce diagonal factor pairs:
4 & 8 \( \div 4 \rightarrow \) 1 & 2
15 & 9 \( \div 3 \rightarrow \) 5 & 3
3 Multiply Across
Multiply simplified numbers:
\( \frac{1 \times 5}{3 \times 2} = \frac{5}{6} \)
Notice how our previous cross-cancelling skills plug straight in once we flip to multiplication!
Class Practice
Your Turn
Problem A Two Fractions
\( \frac{5}{6} \div \frac{2}{3} \)
Solve on your whiteboard or paper. Simplify completely!
Problem B With a Whole Number
\( \frac{7}{10} \div 14 \)
Solve on your whiteboard or paper. Simplify completely!
Strategy Checklist: 1. Keep the first • 2. Change to multiply • 3. Flip to the reciprocal • 4. Cross-cancel!
Cancel 5 & 5 (1, 1); 4 & 6 (2, 3)
\(= -\frac{1 \times 3}{2 \times 1} = \mathbf{-\frac{3}{2}\text{ or }-1\frac{1}{2}}\)
\(\displaystyle {\frac{12}{5} \times \left(-\frac{15}{16}\right)}\)
Cancel 12 & 16 (3, 4); 5 & 15 (1, 3)
\(= -\frac{3 \times 3}{1 \times 4} = \mathbf{-\frac{9}{4}\text{ or }-2\frac{1}{4}}\)
\(\displaystyle {-\frac{10}{3} \times \left(-\frac{9}{20}\right)}\)
Cancel 10 & 20 (1, 2); 3 & 9 (1, 3)
\(= \frac{1 \times 3}{1 \times 2} = \mathbf{\frac{3}{2}\text{ or }1\frac{1}{2}}\)
Answers
\(\frac{3}{2}\) / \(1\frac{1}{2}\)
\(-\frac{2}{3}\)
\(\frac{5}{4}\) / \(1\frac{1}{4}\)
\(-\frac{7}{10}\)
\(-\frac{3}{2}\) / \(-1\frac{1}{2}\)
\(\frac{8}{15}\)
\(\frac{2}{3}\)
\(-\frac{1}{24}\)
\(-\frac{15}{2}\) / \(-7\frac{1}{2}\)
\(-\frac{3}{2}\) / \(-1\frac{1}{2}\)
\(-\frac{9}{4}\) / \(-2\frac{1}{4}\)
\(\frac{3}{2}\) / \(1\frac{1}{2}\)