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3 years ago

If x varies directly with y and y is 10 when x is 8, what is x when y is 18?

2 answers:

swat323 years ago

5 0

Knowing that x varies directly with y, we know the basic skeleton of the equation is y = mx.

To find m, plug in the known coordinate (8,10), where the x-coordinate is 8 and the y-coordinate is 10.
$y=mx \\ 10=m8 \\ (10)/8=(8m)/8 \\ m= \frac{10}{8} = \frac{5}{4}$

Then, plug in m to the equation to get y = (5/4)x.

Finally, plug in the y-coordinate 18 to the equation and solve for x!
$y= \frac{5}{4}x \\ 18= \frac{5}{4}x \\ \frac{4}{5}(18)=( \frac{5}{4}x) \frac{4}{5} \\ x= \frac{4*18}{5} \\ x= \frac{72}{5}$

Your exact answer is x = 72/5. However, if your teacher prefers decimals, then x = 14.4

Hope this helps!

Vesnalui [34]3 years ago

3 0

y varies directly with x
y=kx
10=k(15)
k=10/15
y=(10/15)x
when x=6
y=(10/15)(6)=60/15=4
x varies inversely as y
x=k/y
2=k/8
k=16
x=16/y
when y=17

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A recent study focused on the number of times men and women who live alone buy take-out dinner in a month. Assume that the distr

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Answer:

(a) Decision rule for 0.01 significance level is that we will reject our null hypothesis if the test statistics does not lie between t = -2.651 and t = 2.651.

(b) The value of t test statistics is 1.890.

(c) We conclude that there is no difference in the mean number of times men and women order take-out dinners in a month.

(d) P-value of the test statistics is 0.0662.

Step-by-step explanation:

We are given that a recent study focused on the number of times men and women who live alone buy take-out dinner in a month.

Also, following information is given below;

Statistic : Men Women

The sample mean : 24.51 22.69

Sample standard deviation : 4.48 3.86

Sample size : 35 40

Let $\mu_1$ = mean number of times men order take-out dinners in a month.

$\mu_2$ = mean number of times women order take-out dinners in a month

(a) So, Null Hypothesis, $H_0$ : $\mu_1-\mu_2$ = 0 {means that there is no difference in the mean number of times men and women order take-out dinners in a month}

Alternate Hypothesis, $H_A$ : $\mu_1-\mu_2\neq$ 0 {means that there is difference in the mean number of times men and women order take-out dinners in a month}

The test statistics that would be used here Two-sample t test statistics as we don't know about the population standard deviation;

T.S. = $\frac{(\bar X_1-\bar X_2)-(\mu_1-\mu_2)}{s_p \sqrt{\frac{1}{n_1}+\frac{1}{n_2} } }$ ~ $t__n_1_-_n_2_-_2$

where, $\bar X_1$ = sample mean for men = 24.51

$\bar X_2$ = sample mean for women = 22.69

$s_1$ = sample standard deviation for men = 4.48

$s_2$ = sample standard deviation for women = 3.86

$n_1$ = sample of men = 35

$n_2$ = sample of women = 40

Also, $s_p=\sqrt{\frac{(n_1-1)s_1^{2}+(n_2-1)s_2^{2} }{n_1+n_2-2} }$ = $\sqrt{\frac{(35-1)\times 4.48^{2}+(40-1)\times 3.86^{2} }{35+40-2} }$ = 4.16

So, test statistics = $\frac{(24.51-22.69)-(0)}{4.16 \sqrt{\frac{1}{35}+\frac{1}{40} } }$ ~ $t_7_3$

= 1.890

(b) The value of t test statistics is 1.890.

(c) Now, at 0.01 significance level the t table gives critical values of -2.651 and 2.651 at 73 degree of freedom for two-tailed test.

Since our test statistics lies within the range of critical values of t, so we have insufficient evidence to reject our null hypothesis as it will not fall in the rejection region due to which we fail to reject our null hypothesis.

Therefore, we conclude that there is no difference in the mean number of times men and women order take-out dinners in a month.

(d) Now, the P-value of the test statistics is given by;

P-value = P( $t_7_3$ > 1.89) = 0.0331

So, P-value for two tailed test is = 2 $\times$ 0.0331 = 0.0662