Question

Alicia has 7 paintings she wants to hang side by side on her wall.

Answer 1

The question is an illustration of permutation and combinations.

• The number of ways she can choose 4 out of the 7 paintings is 35
• The number of ways she can arrange 4 out of the 7 paintings is 840

The given parameters are:

$\mathbf{n = 7}$

$\mathbf{r = 4}$

(a) Choose 4 of 7 paintings

Choosing 4 of 7 paintings implies combination.

So, we have:

$\mathbf{^nC_r = \frac{n!}{(n - r)!r!}}$

Substitute values for n and r

$\mathbf{^7C_4 = \frac{7!}{(7 - 4)!4!}}$

$\mathbf{^7C_4 = \frac{7!}{3!4!}}$

Expand

$\mathbf{^7C_4 = \frac{7 \times 6 \times 5 \times 4!}{3 \times 2 \times 1 \times 4 !}}$

$\mathbf{^7C_4 = 35}$

Hence, the number of ways she can choose 4 out of the 7 paintings is 35

(b) Arrange 4 of 7 paintings

Arranging 4 of 7 paintings implies permutation.

So, we have:

$\mathbf{^nP_r = \frac{n!}{(n - r)!}}$

Substitute values for n and r

$\mathbf{^7P_4 = \frac{7!}{(7 - 4)!}}$

$\mathbf{^7P_4 = \frac{7!}{3!}}$

Expand

$\mathbf{^7P_4 = \frac{7 \times 6 \times 5 \times 4 \times 3!}{3!}}$

$\mathbf{^7P_4 = 840}$

Hence, the number of ways she can arrange 4 out of the 7 paintings is 840

Read more about permutation and combinations at:

brainly.com/question/15301090