Plz help! I am so confused and we only just started learning this

The length of a rectangle is 4cm less than twice it’s width the perimeter of the rectangle is 34cm. What are the Demensions of t

serg [7]

Answer:

w=7 and l=10

Step-by-step explanation:

To find the dimensions, create an equation for its perimeter and solve. Recall, the perimeter formula for a rectangle is P = 2l+2w. P is 34 cm. L is 4cm less than twice the width or 2w-4. And the width is w.

P = 2l+2w

34 = 2(2w-4) + 2w

34 = 4w -8 +2w

34 = 6w -8

34+8 = 6w

42 = 6w

7=w

The width is 7 cm. To find the length substitute w=7 into l=2w-4.

l=2w-4

l=2(7)-4

l=14-4

l=10

5 0

3 years ago

Write an equation in slope-intercept form of the line that passes through the given point and is parallel to the graph of the gi

solniwko [45]

Written in slope intercept it would be..

y= -2x^2 + 2x + 18

5 0

3 years ago

Most dermatologists recommend using sunscreens that have a Sun Protection Factor (SPF) of at least 30. One of the authors wanted

Basile [38]

Answer: We are 95% confident that the mean SPF level of sunscreen used by all Cal Poly students is between 29.0813 and 40.0187.

Step-by-step explanation:

Given : Significance level : $\alpha: 1-0.95=0.05$

Sample size : n= 52 , which is a large sample (n>30), so we use z-test.

By using z-value table,

Critical value: $z_{\alpha/2}=1.96$

Sample mean : $\overline{x}= 34.55$

Standard deviation : $\sigma= 20.12$

The confidence interval for population means is given by :-

$\overline{x}\pm z_{\alpha/2}\dfrac{\sigma}{\sqrt{n}}$

i.e. $34.55\pm(1.96)\dfrac{ 20.12}{\sqrt{52}}$

$=34.55\pm5.46867829455\\\\\approx34.55\pm5.4687\\\\=(34.55-5.4687, 34.55+5.4687)=(29.0813,\ 40.0187)$

Now, the 95% confidence interval for the ppopulation mean = . (29.0813, 40.0187)

Hence, We are 95% confident that the mean SPF level of sunscreen used by all Cal Poly students is between 29.0813 and 40.0187.

7 0

2 years ago

The lengths of a certain species of fish are approximately normally distributed with a given mean and standard deviation. Accord

umka21 [38]

Answer:

c) 68%

Step-by-step explanation:

The empirical rule states that most of the data will be within three standard deviations in a normal distribution. The 68% of the data will be within one standard deviation, the 95% will be within two standard deviations, and 99.7% of the data will be within three standard deviations.

A normal distribution is a continuous distribution in which values around the mean are the most frequents. It can also be called a bell-shaped distribution.

5 0

2 years ago

Read 2 more answers

Farmer Ed has 8,000 meters of fencing & wants to enclose a rectangular plot that borders a river. If farmer Ed does not fenc

attashe74 [19]

Answer:

largest area that can be enclosed = 8,000,000 m²

Step-by-step explanation:

Since it is a rectangle plot, the area is expressed as; A = xy, where x is length and y is width.

Because it is next to the river, he only needs to fence three sides, so amount of fencing; F = x + 2y.

Since we know the amount of fencing available is 8000m, we get:

8000 = x + 2y

solving for x, we have;

x = 8000 - 2y

substitute 8000 - 2y for x into the area equation to give;

A = (8000 - 2y)y distribute

A = -2y² + 8000y

Now, due to the negative sign next to 2, this will be a parabola which opens down, meaning that the point of maximum area will be at the vertex,

Thus; y = -b/2a = -8000/[2(-2)] = 2000

x = 8000 - 2(2000) = 4000

A = 4000(2000) = 8,000,000 m²

8 0

3 years ago