Permutations & Combinations
Permutations
Grade 11
Question:
<p>Find the value of <i>r</i>, if <span style="math">\(^{11}P_r = 990\)</span></p>
Step-by-Step Solution
Key Concept: Express the given number as a product of consecutive integers to identify the permutation formula pattern.
<p><strong>Solution:</strong></p><p>Given: <span style="math">$^{11}P_r = 990$</span></p><p>We can express <span style="math">$990 = 11 \times 10 \times 9 = \,^{11}P_3$</span></p><p>Therefore, <span style="math">$r = 3$</span></p>
Correct Answer: 3