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2 years ago

20. The H.M. between 2 and 8 is(1 marks )

Mathematics

1 answer:

e-lub [12.9K]2 years ago

6 0

Answer as an improper fraction = 16/5

Answer as a mixed number = 3 & 1/5

Answer in decimal form = 3.2

All of those values represent the same thing, but written in a different way.

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Explanation:

I'm assuming HM stands for Harmonic Mean in this case.

If so, then we apply the reciprocal operation to each value to get 1/2 and 1/8 (from 2 and 8 respectively).

Add up those fractions:

1/2 + 1/8 = 4/8 + 1/8 = 5/8

Now we'll divide n = 2 over that result. The n = 2 refers to the number of items in the original set.

n divide over (5/8) = 2*(8/5) = 16/5 which is the answer as an improper fraction

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To convert to a mixed number, we can do the following:

16/5 = (15+1)/5

16/5 = 15/5 + 1/5

16/5 = 3 + 1/5

16/5 = 3 & 1/5

Or if you need the answer in decimal form, then using a calculator would get you 16/5 = 3.2

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A college student is interested in investigating the TV-watching habits of her classmates and surveys 20 people on the number of

Alla [95]

Answer:

80% confidence interval of the true average number of hours of TV watched per week is [8.28 hours, 11.02 hours].

Step-by-step explanation:

We are given that a college student is interested in investigating the TV-watching habits of her classmates and surveys 20 people on the number of hours they watch per week. The results are provided below;

Hours of TV per week (X): 6, 14, 13, 6, 16, 10, 19, 4, 5, 5, 18, 8, 7, 14, 8, 8, 9, 12, 6, 5.

Firstly, the Pivotal quantity for 80% confidence interval for the true average is given by;

P.Q. = $\frac{\bar X-\mu}{\frac{s}{\sqrt{n} } }$ ~ $t_n_-_1$

where, $\bar X$ = sample mean number of hours of TV watched per week = $\frac{\sum X}{n}$ = 9.65

s = sample standard deviation = $\sqrt{\frac{\sum (X -\bar X)^{2} }{n-1} }$ = 4.61

n = sample of people = 20

$\mu$ = true average number of hours of TV watched per week

Here for constructing 80% confidence interval we have used One-sample t-test statistics as we don't know about population standard deviation.

So, 80% confidence interval for the true average, $\mu$ is ;

P(-1.33 < $t_1_9$ < 1.33) = 0.80 {As the critical value of t at 19 degrees of

freedom are -1.33 & 1.33 with P = 10%}

P(-1.33 < $\frac{\bar X-\mu}{\frac{s}{\sqrt{n} } }$ < 1.33) = 0.80

P( $-1.33 \times {\frac{s}{\sqrt{n} } }$ < ${\bar X-\mu}$ < $1.33 \times {\frac{s}{\sqrt{n} } }$ ) = 0.80

P( $\bar X-1.33 \times {\frac{s}{\sqrt{n} } }$ < $\mu$ < $\bar X+1.33 \times {\frac{s}{\sqrt{n} } }$ ) = 0.80

80% confidence interval for $\mu$ = [ $\bar X-1.33 \times {\frac{s}{\sqrt{n} } }$ , $\bar X+1.33 \times {\frac{s}{\sqrt{n} } }$ ]

= [ $9.65-1.33 \times {\frac{4.61}{\sqrt{20} } }$ , $9.65+1.33 \times {\frac{4.61}{\sqrt{20} } }$ ]

= [8.28 hours, 11.02 hours]

Therefore, 80% confidence interval of the true average number of hours of TV watched per week is [8.28 hours, 11.02 hours].

7 0

2 years ago

You find 72 coins consisting only of nickels, dimes, and quarters, with a face value of $10.20. However, the coins all date from

Oliga [24]

Answer:

You have found 24 nickels.

Step-by-step explanation:

Let N be the number of nickles, D be the number of dimes and Q be the number of quarters. The number of coins and their face values are given by the following expressions, respectively:

$N+D+Q=72\\0.05N+0.10D+0.25Q=10.20$

As of now we have three variables and two expressions, the final expression needed to solve the linear system is given by the amount offered by the coin dealer:

$10N+20D+15Q=1,060$

Solving the linear system:

$N+D+Q=72\\5N+10D+25Q=1,020\\10N+20D+15Q=1,060\\\\10N-10N+20D-20D+15Q-50Q=1,060-(2*1,020)\\-35Q=-980\\Q=28\\\\5N-10N+10D-10D+25Q-10Q=1,020-720\\-5N+15Q=300\\-5N=300-(15*28)\\N=24$

You have found 24 nickels.

7 0

2 years ago

Simplify: 5a + 1r + 2a + 4r

Marina CMI [18]

Answer:

7a+5r

Step-by-step explanation:

5a + 1r + 2a + 4r

add like terms

7a+5r

hope that helps

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2 years ago

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2 years ago

20. The H.M. between 2 and 8 is(1 marks )​

20. The H.M. between 2 and 8 is(1 marks )