Question

A special type of door lock has a panel with five buttons labeled with the digits 1 through 5. This lock is opened by a sequence of three actions. Each action consists of either pressing one of the buttons or pressing a pair of them simultaneously.

Answer 1

There are several ways the door can be locked, these ways illustrate combination.

There are 3375 possible combinations

From the question, we have:

$\mathbf{n = 5}$ --- the number of digits

$\mathbf{r = 3}$ ---- the number of actions

Each of the three actions can either be:

• Pressing one button
• Pressing a pair of buttons

The number of ways of pressing a button is:

$\mathbf{n_1 = ^5C_1}$

Apply combination formula

$\mathbf{n_1 = \frac{5!}{(5-1)!1!}}$

$\mathbf{n_1 = \frac{5!}{4!1!}}$

$\mathbf{n_1 = \frac{5 \times 4!}{4! \times 1}}$

$\mathbf{n_1 = 5}$

The number of ways of pressing a pair is:

$\mathbf{n_2 = ^5C_2}$

Apply combination formula

$\mathbf{n_2 = \frac{5!}{(5-2)!2!}}$

$\mathbf{n_2 = \frac{5!}{3!2!}}$

$\mathbf{n_2 = \frac{5 \times 4 \times 3!}{3! \times 2 \times 1}}$

$\mathbf{n_2 = 10}$

So, the number of ways of performing one action is:

$\mathbf{n =n_1 + n_2}$

$\mathbf{n =5 + 10}$

$\mathbf{n =15}$

For the three actions, the number of ways is:

$\mathbf{Action = n^3}$

$\mathbf{Action = 15^3}$

$\mathbf{Action = 3375}$

Hence, there are 3375 possible combinations

Read more about permutation and combination at:

brainly.com/question/4546043