assume that when adults with smartphones are randomly selected 15 use them in meetings or classes if 15 adult smartphones are randomly selected, find the probability that at least 4 of them use their smartphones

The probability that at least 4 of them use their smartphones is 0.1773.

Step-by-step explanation:

We are given that when adults with smartphones are randomly selected 15% use them in meetings or classes.

Also, 15 adult smartphones are randomly selected.

Let X = Number of adults who use their smartphones

The above situation can be represented through the binomial distribution;

where, n = number of trials (samples) taken = 15 adult smartphones

           r = number of success = at least 4

           p = probability of success which in our question is the % of adults

                 who use them in meetings or classes, i.e. 15%.

So, X ~ Binom(n = 15, p = 0.15)

Now, the probability that at least 4 of them use their smartphones is given by = P(X 4)

P(X 4) = 1 - P(X = 0) - P(X = 1) - P(X = 2) - P(X = 3)

=

=

= 0.1773

Answer

5 and -4

Explanation

If the two triangle are congruent then they have the same area.

20 = x² - x

x² - x - 20 = 0

x² - x + (1/2)² = 20 + (1/2)²

(x - 1/2)² = 20.25

x - 1/2 = √20.25

x - 1/2 = 4.5                             or    x - 1/2 = - 4.5

x = 4 1/2 + 1/2                                      x = -4 1/2 + 1/2

   = 5                                                      = -4

The values of x are 5 and -4.