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ikadub [295]
3 years ago
5

There are 21 students in a class. The ratio of the number of boys to the number of girls is 4:3. How many girls are in the class

?
Mathematics
2 answers:
ZanzabumX [31]3 years ago
8 0

Answer:

Step-by-step explanation:

4:3 total is 7

8:6 total is 14

12:9 total is 21

So there are 9 girls.

k0ka [10]3 years ago
4 0

Answer: 9

Step-by-step explanation:

Given : There are 21 students in a class.

It is given that the ratio of the number of boys to the number of girls is 4:3.

Let 4x be the number of boys and 3x be the number of girls in class.

According to the question , we have

3x+4x=21\\\\\Rightarrow\ 7x=21\\\\\Rightarrow\ x=\dfrac{21}{7}=3

Now, the number of girls in class = 3x= 3(3)=9

Hence, there are 9 girls in class.

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In a random sample of 380 cars driven at low altitudes, 42 of them exceeded a standard of 10 grams of particulate pollution per
alexdok [17]

Answer:

The test statistic for testing if the proportion of high-altitude vehicles exceeding the standard is greater than the proportion of low-altitude vehicles exceeding the standard is 3.234.

Step-by-step explanation:

We are given that in a random sample of 380 cars driven at low altitudes, 42 of them exceeded a standard of 10 grams of particulate pollution per gallon of fuel consumed.

In an independent random sample of 90 cars driven at high altitudes, 24 of them exceeded the standard.

Let p_1 = <u><em>population proportion of cars driven at high altitudes who exceeded a standard of 10 grams</em></u>.

p_2 = <u><em>population proportion of cars driven at low altitudes who exceeded a standard of 10 grams</em></u>.

So, Null Hypothesis, H_0 : p_1\leq p_2      {means that the proportion of high-altitude vehicles exceeding the standard is smaller than or equal to the proportion of low-altitude vehicles exceeding the standard}

Alternate Hypothesis, H_A : p_1>p_2      {means that the proportion of high-altitude vehicles exceeding the standard is greater than the proportion of low-altitude vehicles exceeding the standard}

The test statistics that will be used here is <u>Two-sample z-test statistics</u> for proportions;

                             T.S.  =  \frac{(\hat p_1-\hat p_2)-(p_1-p_2)}{\sqrt{\frac{\hat p_1(1-\hat p_1)}{n_1}+\frac{\hat p_2(1-\hat p_2)}{n_2} } }  ~  N(0,1)

where, \hat p_1 = sample proportion of cars driven at high altitudes who exceeded a standard of 10 grams = \frac{24}{90} = 0.27

\hat p_2 = sample proportion of cars driven at low altitudes who exceeded a standard of 10 grams = \frac{42}{380} = 0.11

n_1 = sample of cars driven at high altitudes = 90

n_2 = sample of cars driven at low altitudes = 380

So, the test statistics =  \frac{(0.27-0.11)-(0)}{\sqrt{\frac{0.27(1-0.27)}{90}+\frac{0.11(1-0.11)}{380} } }      

                                   =  3.234

The value of z-test statistics is 3.234.

7 0
3 years ago
What is X? 3x - 24 = 81
Arturiano [62]

Answer:

35 would be your answer

Step-by-step explanation:

3x-24=81

So first off, add 24 to 24 and 81

You would get 3=105

Now divide 3/3 and 105/3 which will get you 35!

Hopefully this helps!

6 0
2 years ago
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