Answer:
16.78% probability that exactly 12 of them use their smartphones in meetings or classes.
Step-by-step explanation:
For each adult, there are only two possible outcomes. Either they use their smartphone in meetings or classes, or they do not. The probability of a person using their phone in meetings or classes is independent of any other person. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
In which 
is the number of different combinations of x objects from a set of n elements, given by the following formula.
And p is the probability of X happening.
64% use them in meetings or classes.
This means that 
20 adult smartphone users are randomly selected
This means that 
Probability that exactly 12 of them use their smartphones in meetings or classes.
This is P(X = 12).
16.78% probability that exactly 12 of them use their smartphones in meetings or classes.
Answer:
5 years
Step-by-step explanation:
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Answer:
<em>37%</em>
Step-by-step explanation:
Add up the percentages and subtract them by 1.00:
- 35% & 28% = 0.35 & 0.28
- 0.35 + 0.28 = 0.63
- 1.00 - 0.63 = 0.37
- 0.37 = 37%
Good luck! :)
Answer: Joe hit the target 4 times.
Explanation: We can write this scenario as a system of equations.
Let’s express the number of times he hits the target with x.
Let’s express the number of times he misses the target with y.
“He earned 20 points each time he hit the target but lost 50 points when he miss. Joe ended the night with negative 470 points...”
20x - 50y = -470
“...after 15 shots.”
x + y = 15
Let’s write the whole system of equations.
20x - 50y = -470
x + y = 15
Let’s solve the second equation for y.
x + y = 15
Subtract x from both sides.
y = 15 - x
Let’s substitute y in the first equation with 15 - x.
20x - 50(15 - x) = -470
Distribute -50 among 15 and -x in the term -50(15 - x).
20x - 750 + 50x = -470
Combine like terms on the left side.
70x - 750 = -470
Add 750 on both sides.
70x = 280
Divide both sides by 70.
x = 4
Since we know that x = 4, we know that Joe hit the target 4 times.
