Sarah can drive her car 12 miles using 1/3 gallon of gas. How many miles can she drive on one gallon of gas?

This is a Differential Equations problem, I only need help on part 1 from question five. I need steps as well, thank you.

jolli1 [7]

Answer:

a) $y(t) = \sqrt{2t + 1 }$

b) 1.5 hours after thickness will be 2 inches.

Step-by-step explanation:

$\frac{dy}{dt} = \frac{1}{y} \\ \\ ydy = dt \\ \\ integrating \: both \: sides \\ \\ \int y \: dy = \int 1 \: dt \\ \\ \frac{ {y}^{2} }{2} = t + c \\ \\ {y}^{2} = 2t + 2c \\ \\ y (t)= \sqrt{2t + 2c} ...(1) \\ \\ a) \: \: \: plug \: t = 0 \: in \: (1) \\ \\ y (0)= \sqrt{2(0) +2 c} \\ \\ y (0)= \sqrt{0 +2 c} \\ \\ 1 = \sqrt{2c} \: \: ( \because \: y (0)=1) \\ \\ 2c = 1 \: \implies \: c = \frac{1}{2} \\ \\ plug \: c = \frac{1}{2} \: in \: (1) \\ \\ y(t) = \sqrt{2t + 2 \times \frac{1}{2} } \\ \\ \huge \: \red {y(t) = \sqrt{2t + 1 } } \\ \\b) \: \: plug \: y(t) = 2 \: in \: above \: equation \\ \\ 2 = \sqrt{2t + 1} \\ \\ 4 = 2t + 1 \: \\ (squaring \: both \: sides) \\ \\ 4 - 1 = 2t \\ \\ 2t = 3 \\ \\ t = \frac{3}{2} \\ \\ t = 1.5 \: hours \\$

6 0

2 years ago

In the past, 21% of all homes with a stay-at-home parent, the father is the stay-at-home parent. An independent research firm ha

Afina-wow [57]

Answer:

A sample size of 79 is needed.

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of $\pi$ , and a confidence level of $1-\alpha$ , we have the following confidence interval of proportions.

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which

z is the zscore that has a pvalue of $1 - \frac{\alpha}{2}$ .

For this problem, we have that:

$\pi = 0.21$

The margin of error is:

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

95% confidence level

So $\alpha = 0.05$ , z is the value of Z that has a pvalue of $1 - \frac{0.05}{2} = 0.975$ , so $Z = 1.96$ .

What sample size is needed if the research firm's goal is to estimate the current proportion of homes with a stay-at-home parent in which the father is the stay-at-home parent with a margin of error of 0.09?

A sample size of n is needed.

n is found when M = 0.09. So

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

$0.09 = 1.96\sqrt{\frac{0.21*0.79}{n}}$