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3 years ago

What is the total surface area of a cylinder whose length is twice the radius

1 answer:

7 0

Lateral surface area of a cylinder: 2πrh, r is the radius, h is the height.
area of the top and bottom circle: πr²
when h=2r, the total surface area is:
2πr(2r)+πr²+πr²=6πr²
the answer is 6πr²

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he value of y varies directly with the value of x. When y = 32.5, x = 5. What is the value of y when x = 10? A) 1.5 B) 2.2 C) 37

xz_007 [3.2K]

Answer:

D) 65

Step-by-step explanation:

The formula for direct variation is

y = kx

where k is the constant of variation.

If we know y=32.5 and x=5, we can substitute in to calculate k

32.5 = k * 5

Divide each side by 5

32.5/5 = k

6.5 = k

So the equation is

y = 6.5k

Given x =10

y = 6.5*10

y = 65

7 0

3 years ago

Read 2 more answers

Joanna buys a table and 2 chairs. She receives a 25% discount for being a preferred customer and then pays 6% sales tax on the d

Scrat [10]

The total purchase price is $ 357.75

Solution:

Joanna buys a table and 2 chairs

Cost of table = $ 250

Cost of 1 chair = $ 100

Therefore, cost of a table and 2 chairs = 250 + 2(100) = 450

Thus, cost price = $ 450

She receives a 25% discount for being a preferred customer

Therefore, discount = 25 % of cost price

$discount = 25 \% \times 450\\\\discount = \frac{25}{100} \times 450\\\\discount = 0.25 \times 450 = 112.5$

Thus, amount after discount = cost price - discount

amount after discount = 450 - 112.5 = 337.5

Thus, amount after discount is $ 337.5

Then pays 6% sales tax on the discounted purchase price

Sales tax = 6 % of 337.5

$sales\ tax = 6 \% \times 337.5\\\\sales\ tax = \frac{6}{100} \times 337.5\\\\sales\ tax = 20.25$

Thus, total purchase price is given as:

total purchase price = Amount after discount + sales tax

total purchase price = 337.5 + 20.25 = 357.75

Thus total purchase price is $ 357.75

4 0

3 years ago

Two catalysts may be used in a batch chemical process. Twelve batches were prepared using catalyst 1, resulting in an average yi

aalyn [17]

Answer:

a) $t=\frac{(91-85)-(0)}{2.490\sqrt{\frac{1}{12}}+\frac{1}{15}}=6.222$

$df=12+15-2=25$

$p_v =P(t_{25}>6.222) =8.26x10^{-7}$

So with the p value obtained and using the significance level given $\alpha=0.01$ we have $p_v$ so we can conclude that we have enough evidence to reject the null hypothesis.

b) $(91-85) -2.79 *2.490 \sqrt{\frac{1}{12} +\frac{1}{15}} =3.309$

$(91-85) +2.79 *2.490 \sqrt{\frac{1}{12} +\frac{1}{15}} =8.691$

Step-by-step explanation:

Notation and hypothesis

When we have two independent samples from two normal distributions with equal variances we are assuming that

$\sigma^2_1 =\sigma^2_2 =\sigma^2$

And the statistic is given by this formula:

$t=\frac{(\bar X_1 -\bar X_2)-(\mu_{1}-\mu_2)}{S_p\sqrt{\frac{1}{n_1}}+\frac{1}{n_2}}$

Where t follows a t distribution with $n_1+n_2 -2$ degrees of freedom and the pooled variance $S^2_p$ is given by this formula:

$\S^2_p =\frac{(n_1-1)S^2_1 +(n_2 -1)S^2_2}{n_1 +n_2 -2}$

This last one is an unbiased estimator of the common variance $\sigma^2$

Part a

The system of hypothesis on this case are:

Null hypothesis: $\mu_2 \leq \mu_1$

Alternative hypothesis: $\mu_2 > \mu_1$

Or equivalently:

Null hypothesis: $\mu_2 - \mu_1 \leq 0$

Alternative hypothesis: $\mu_2 -\mu_1 > 0$

Our notation on this case :

$n_1 =12$ represent the sample size for group 1

$n_2 =15$ represent the sample size for group 2

$\bar X_1 =85$ represent the sample mean for the group 1

$\bar X_2 =91$ represent the sample mean for the group 2

$s_1=3$ represent the sample standard deviation for group 1

$s_2=2$ represent the sample standard deviation for group 2

First we can begin finding the pooled variance:

$\S^2_p =\frac{(12-1)(3)^2 +(15 -1)(2)^2}{12 +15 -2}=6.2$

And the deviation would be just the square root of the variance:

$S_p=2.490$

Calculate the statistic

And now we can calculate the statistic:

$t=\frac{(91-85)-(0)}{2.490\sqrt{\frac{1}{12}}+\frac{1}{15}}=6.222$

Now we can calculate the degrees of freedom given by:

$df=12+15-2=25$

Calculate the p value

And now we can calculate the p value using the altenative hypothesis:

$p_v =P(t_{25}>6.222) =8.26x10^{-7}$

Conclusion

So with the p value obtained and using the significance level given $\alpha=0.01$ we have $p_v$ so we can conclude that we have enough evidence to reject the null hypothesis.

Part b

For this case the confidence interval is given by:

$(\bar X_1 -\bar X_2) \pm t_{\alpha/2} S_p \sqrt{\frac{1}{n_1} +\frac{1}{n_2}}$

For the 99% of confidence we have $\alpha=1-0.99 = 0.01$ and $\alpha/2 =0.005$ and the critical value with 25 degrees of freedom on the t distribution is $t_{\alpha/2}= 2.79$