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hodyreva [135]
2 years ago
8

A scientist wishes to estimate the mean breaking strength of a certain type of steel rod within 3.0 psi with 95% confidence. Bas

ed on experience with a similar type of steel, she believes the standard deviation is approximately 15.0 psi in individual breaking strengths. How many steel rods should she test?
Mathematics
1 answer:
yaroslaw [1]2 years ago
6 0

Answer:97 rods

Step-by-step explanation:

The number of steel rods for 95% confidence level

n=\left ( \frac{Z_\frac{\alpha }{2}\times \hat{\sigma }}{E} \right )^2

Z_\frac{\alpha }{2}=1.96

E=3

\hat{\sigma }=15

Substituting values

n=\left ( \frac{1.96\times 15}{3}\right )^2

n=96.04\approx 97

Thus 97 rods is tested

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The farthest distance on the planet that the eye can see is given by the formula d=\sqrt{8,000h_1} + \sqrt{8,000h_2}

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2 years ago
Jonathan borrowed $475 at a simple annual interest rate of 2%. How many years will it take him to repay the loan if he wants to
vovikov84 [41]
Firstly you would times 475 by the percentage, which you can convert to a decimal my multiplying the percentage by 100.

475 * 0.02 = 9.50

Then divide the interest by the amount of interest per year:
38 / 9.5 = 4.

The answer would be 4 years.

Hope this helps.
3 0
2 years ago
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Garth has x books which is 20 more books than Henrietta has. If Garth gives Henrietta 7 books how many books does Henrietta now
hammer [34]

Answer:

she should have x-27 books left

Step-by-step explanation:

7 0
2 years ago
Nico and Albert are finishing up a science project. They measured the length in inches of three insects. They also found the ave
atroni [7]

Answer:

Step-by-step explanation:

Given the length of the bugs as shown;

Lady bug = 3/8

Ant = 1/4

Firefly = 7/8

Honey bee = 0.8

Deer tick = 0.2

Before we arrange the length in ascending order (shortest to longest), we will have to represent them in percentage.

Lady bug = 3/8×100

= 300/8

= 37.5%

Ant = 1/4×100

Ant = 25%

Firefly = 7/8 × 100

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Honey bee = 0.8×100

Honey bee = 80%

Deer tick = 0.2×100

Deer tick = 20%

On rearranging in ascending order:

20%, 25%, 37.5%, 80%, 87.5%

Based on the insect

Deer tick, Ant, ladybug, honey bee, Firefly

Based on their length:

0.2, 1/4, 3/8, 0.8, 7/8

5 0
2 years ago
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A salesman used three types of order forms: A, B, C. He used 40 of Form A. Of Form B he used four times as many as Form A plus 1
aivan3 [116]

Answer:

a. 440

Step-by-step explanation:

The information provided allows us to set up the following system of linear equations:

A = 40\\B=4A+0.5C\\C=A+0.5B

We already have the value for A, solving the system gives us the values for B and C:

A = 40\\B=(4*40)+0.5C\\C=40+0.5B\\\\B -B-80 = (4*40)+0.5C-2C\\C=\frac{160+80}{1.5}\\C=160\\B= (4*40) +(0.5*160)\\B=240

The total number of forms used is:

A+B+C = 40+240+160 = 440

He used 440 forms.

4 0
2 years ago
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