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almond37 [142]
3 years ago
6

36) The speed of a boat in still water is 5km/hr. If the speed of the boat against the stream is 3

Mathematics
1 answer:
Radda [10]3 years ago
5 0

Answer:

2km/hr

Step-by-step explanation:

Given the following

Speed of boat in water = 5km/hr

Speed of boat against stream = 3km/hr

Since the speed of boat is going against that of the stream, hence, the speed of the stream will be the difference between the speed of boat and that when the boat is against the stream

Speed of stream = 5km/hr - 3km/hr

Speed of stream = 2km/hr

hence the required speed of stream is 2km/hr

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Allen�s hummingbird (Selasphorus sasin ) has been studied by zoologist Bill Alther A small group of 15 Allen� s hummingbirds has
Bogdan [553]

Answer:

1) 80% CI: [3.04; 3.26]gr

d= 0.11

2) n= 28 hummingbirds

Step-by-step explanation:

Hello!

The study variable of this experiment is:

X: the weight of a hummingbird. (gr)

And it has a normal distribution, symbolically: X~N(μ;σ²)

And (I hope I got it correctly) its population standard deviation is σ= 0.33

There was a sample of n= 15 hummingbirds taken, its sample mean X[bar]= 3.15 gr

1) You need to construct an 80% Confidence Interval for the population mean of the hummingbird's weight.

Since the study variable has a normal distribution, you can use either the standard normal distribution or the Student's t distribution. Both are useful to estimate the population mean. Since the population standard variance is known, the best choice is the Standard normal.

Z= <u> X[bar] - μ </u>~ N(0;1)

       σ/√n

The formula for the interval is:

X[bar] ± Z_{1- \alpha /2} * (σ/√n)

Z_{1- \alpha /2}= Z_{0.90} = 1.28

3.15 ± 1.28 * (0.33/√15)

[3.04; 3.26]gr

The margin of error (d) of a confidence interval is hal its amplitude (a)

a= Upper bond - Lower bond

d= (Upper bond - Lower bond)/2

d= \frac{(3.26-3.04)}{2} = 0.11

2) You need to calculate a sample size for a 80% Confidence interval for the average weight of the hummingbirds with a margin of error of d= 0.08

As I said before, the margin of error is half the amplitude of the interval, the formula you use to estimate the population mean has the following structure:

"point estamator" ± "margin of error"

Then the margin of error is:

d= Z_{1- \alpha /2} * (σ/√n)

Now what you have to do is rewrite the formula based on the sample size

d= Z_{1- \alpha /2} * (σ/√n)

\frac{d}{Z_{1- \alpha /2}}= σ/√n

√n * \frac{d}{Z_{1- \alpha /2}}= σ

√n = σ * \frac{Z_1- \alpha /2}{d}

n = (σ * \frac{Z_1- \alpha /2}{d})²

n=  (0.33 * \frac{1.28}{0.08})²

n= 27.8784 ≅ 28 hummingbirds.

I hope it helps!

4 0
3 years ago
A semi circle is drawn on to one of the shorter sides of the rectangle the shorter side of the rectangle measures 4 cm the area
tino4ka555 [31]

Answer:

I dont know I also need help with this

Step-by-step explanation:

this is so hard please help

3 0
2 years ago
Read 2 more answers
I’ll give brainliest , 7th grade work .
Katen [24]

Answer:

In order to properly answer this, we need to know the measurement of the pool in meters

Step-by-step explanation:

3 0
3 years ago
Read 2 more answers
Date
ss7ja [257]

Answer:

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7 0
3 years ago
Why do whole numbers with an exponent get bigger while fractions with an exponent get smaller.
ohaa [14]

Raising a whole number to a power means: 

             Take (a number of things) a number of times, and then possibly
             take that big number of things a number of times again.

Raising a fraction to an exponent means: 

             Take a piece of (a piece of one thing), and then possibly
              take just a piece of that smaller piece.


8 0
3 years ago
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