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aev [14]
3 years ago
12

Sally can detail a car in 50 minutes. Manny does the same job in 35 minutes. How long will it take them to detail a car working

together
Mathematics
1 answer:
Debora [2.8K]3 years ago
3 0

<u>Answer:</u>

Both Sally ans Manny can detail a car in 20.6 min.

<u>Solution: </u>

Let us assume that together they will take total x minutes to detail the car.

Sally detail the car in 50 min.

So in 1 min sally can detail \left(\frac{1}{50}\right) of the car.

Hence in x min sally can detail \left(\frac{x}{50}\right) of the car.

Manny can detail a car in 35 min.

So in 1 min many can detail \left(\frac{1}{35}\right) of the car.

Hence in x min Manny can detail \left(\frac{x}{35}\right) of the car.

So we can say,

\left(\frac{x}{50}\right)+\left(\frac{x}{35}\right)=1

x\left(\frac{1}{50}+\frac{1}{35}\right)=1

x\left(\frac{7+10}{350}\right)=1

\left(\frac{17 x}{350}\right)=1

17 x=350

x=\left(\frac{350}{17}\right)=20.5 8\approx 20.6

So, both of them can detail a car in 20.6 min.

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In a random sample of 1066 U.S. adults, 580 think that the U.S. government
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Answer:

Step-by-step explanation:

This is a test of 2 population proportions. Let 1 and 2 be the subscript for the adults who think that the U.S. government is doing too little to protect the environment presently and the adults who think that the U.S. government is doing too little to protect the environment 10 years ago. The population proportions would be p1 and p2 respectively.

p1 - p2 = difference in the proportion of adults who think that the U.S. government is doing too little to protect the environment presently and the adults who think that the U.S. government is doing too little to protect the environment 10 years ago.

The null hypothesis is

H0 : p1 = p2

p1 - p2 = 0

The alternative hypothesis is

Ha : p1 ≠ p2

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it is a two tailed test

Sample proportion = x/n

Where

x represents number of success

n represents number of samples

For the present,

x1 = 580

n1 = 1066

p1 = 580/1066 = 0.54

For 10 years ago,

x2 = 514

n2 = 1038

P2 = 514/1038 = 0.5

The pooled proportion, pc is

pc = (x1 + x2)/(n1 + n2)

pc = (580 + 514)/(1066 + 1038) = 0.52

1 - pc = 1 - 0.52 = 0.48

z = (p1 - p2)/√pc(1 - pc)(1/n1 + 1/n2)

z = (0.54 - 0.5)/√(0.52)(0.48)(1/1066 + 1/1038) = 0.04/0.02178551744

z = 1.84

Since it is a two tailed test, the curve is symmetrical. We will look at the area in both tails. Since it is showing in one tail only, we would double the area

From the normal distribution table, the area above the test z score in the right tail 1 - 0.967 = 0.033

We would double this area to include the area in the left tail of z = - 1.84 Thus

p = 0.033 × 2 = 0.066

Alpha = 0.1

Since alpha, 0.1 > p value 0.066, we would reject the null hypothesis.

Therefore, at a = 0.10, we can reject the

claim that the proportion of U.S. adults who think that the U.S. government

is doing too little to protect the environment has not changed.

4 0
3 years ago
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