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2 years ago

The probability of being a girl in this class is 4/7 and there are 12 boys. Find the total number of students.

Mathematics

1 answer:

vladimir1956 [14]2 years ago

3 0

Answer: 28 students

Step-by-step explanation:

The probability of being a girl is 4/7 which means that the probability of being a boy is 3/7 as the fractions must add up to 1.

Assuming the number of people in class is x then the following expression can be used to solve for it;

$\frac{3}{7} x = 12\\\\3x = 12 * 7\\\\x = \frac{12 * 7 }{3} \\\\x = 28$

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The article "Occurrence and Distribution of Ammonium in Iowa Groundwater" (K. Schilling, Water Environment Research, 2002:177–18

Papessa [141]

Answer: 95% confidence interval for the difference between the proportions would be (1.31, 1.39).

Step-by-step explanation:

Since we have given that

Number of alluvial wells = 349

Number of quaternary wells = 143

Number of alluvial wells that had concentrations above 0.1 = 182

Number of quaternary wells that had concentrations above 0.1 = 112

Average of alluvial wells = 0.27

Standard deviation = 0.4

Average of quaternary wells = 1.62

Standard deviation =1.70

So, 95% confidence interval gives

alpha = 5% level of significance.

$\dfrac{\alpha}{2}=2.5\%\\\\z_{\frac{\alpha}{2}}=1.96$

So, 95% confidence interval becomes,

$(1.62-0.27)\pm 1.96\sqrt{\dfrac{0.4^2}{349}+\dfrac{1.7^2}{143}}\\\\=1.35\pm 1.96\times 0.020\\\\=(1.35-0.040,1.35+0.040)\\\\=(1.31,1.39)$

Hence, 95% confidence interval for the difference between the proportions would be (1.31, 1.39).

6 0

3 years ago

Which of the following systems describes the graph ?

Gnoma [55]

Answer:

x > -3 and y ≥ 1/2x - 2

Step-by-step explanation:

blue line = x > -3

red line = pass (0, -2) (4, 0)

y = 1/2x - 2

HOPE THIS HELPS AND HAVE A NICE DAY <3

7 0

1 year ago

Round 7219 to the nearest thousand

elixir [45]

7000 because if the hundred next to the thousand is below 5 the number will be the same
eg: 3200 the answer will be 3000

but if the number is 5 and higher the thousand will be one extra
eg 1: 3521 the answer will be 4000
eg 2: 4809 the answer will be 5000

8 0

3 years ago

Write the equation of the line that is perpendicular to the liney=-1x/ 3 + 2 and goes through the point (5, 6)

KIM [24]

Answer:

y = 3x-9

Step-by-step explanation:

y = -1/3 x +2

The slope is -1/3

We want a line perpendicular to it

Perpendicular lines have negative reciprocal slopes

The new slope is -(-3/1) = 3

We have a slope m=3 and a point (5,6)

We will use point slope form to find the line

y-y-1 = m(x-x1)

y-6 = 3(x-5)

In slope intercept form

Distribute

y-6 = 3x-15

Add 6 to each side

y-6+6 = 3x-15+6

y = 3x-9

3 0

3 years ago

Recall what you know about similarity. If circle B is similar to circle A, what must exist?

Arlecino [84]

Answer:

circle a and circle b must exist

Step-by-step explanation:is circle a and circle b did not exist this question would not be one

7 0

3 years ago