Math Problem Statement

Evaluate the following expression. Express your answer as a fraction or a decimal number rounded to four decimal places.

11C7/11P3

Solution

To evaluate the expression 11C711P3\frac{{11C7}}{{11P3}}, we need to first compute 11C711C7 and 11P311P3.

Step 1: Compute 11C711C7

The combination formula nCknCk is given by:

nCk=n!k!(nk)!nCk = \frac{{n!}}{{k!(n-k)!}}

For 11C711C7, we substitute n=11n = 11 and k=7k = 7:

11C7=11!7!(117)!=11!7!4!11C7 = \frac{{11!}}{{7!(11-7)!}} = \frac{{11!}}{{7!4!}}

Now, calculating the factorials:

11!=11×10×9×8×7!11! = 11 \times 10 \times 9 \times 8 \times 7!

The 7!7! cancels out:

11C7=11×10×9×84!=11×10×9×824=792024=33011C7 = \frac{{11 \times 10 \times 9 \times 8}}{{4!}} = \frac{{11 \times 10 \times 9 \times 8}}{{24}} = \frac{{7920}}{{24}} = 330

So, 11C7=33011C7 = 330.

Step 2: Compute 11P311P3

The permutation formula nPknPk is given by:

nPk=n!(nk)!nPk = \frac{{n!}}{{(n-k)!}}

For 11P311P3, we substitute n=11n = 11 and k=3k = 3:

11P3=11!(113)!=11!8!11P3 = \frac{{11!}}{{(11-3)!}} = \frac{{11!}}{{8!}}

Now, calculating the factorials:

11!=11×10×9×8!11! = 11 \times 10 \times 9 \times 8!

The 8!8! cancels out:

11P3=11×10×9=99011P3 = 11 \times 10 \times 9 = 990

So, 11P3=99011P3 = 990.

Step 3: Compute the final expression

Now we substitute the values of 11C711C7 and 11P311P3:

11C711P3=330990=130.3333\frac{{11C7}}{{11P3}} = \frac{{330}}{{990}} = \frac{1}{3} \approx 0.3333

Thus, the value of the expression is 13\frac{1}{3} or 0.33330.3333.


Do you want more details or have any questions?

Here are 5 related questions you might find interesting:

  1. What is the difference between combinations and permutations?
  2. How would the result change if the expression was 12C812P4\frac{12C8}{12P4}?
  3. Can you explain how factorials play a role in counting combinations and permutations?
  4. What is 11C411C4 and how does it relate to 11C711C7?
  5. How can you generalize the combination and permutation formulas for any nn and kk?

Tip: When working with combinations and permutations, simplify factorials by canceling common terms to make calculations easier!

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Math Problem Analysis

Mathematical Concepts

Combinations
Permutations
Factorials
Basic Arithmetic

Formulas

nCk = n! / (k!(n-k)!)
nPk = n! / (n-k)!

Theorems

The combination formula
The permutation formula

Suitable Grade Level

Grades 10-12