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WITCHER [35]
3 years ago
13

The difference of two numbers, a and b, is 21. The difference of 5 times a and two times b is 18. What are the values of a and b

? A. 4,1 B. -19,40 B. 20,1 C. 30,9 D. -8,-29
Mathematics
1 answer:
PSYCHO15rus [73]3 years ago
6 0
A-b=21
5a-2b=18

We can use substitution here. Take the first equation and solve for A. (Picking this one because it's easy)

a = 21+b

Plugin to the second equation:5(21+b)-2b=18
Simplify: 105 + 5b - 2b = 18
Simplify: 105 + 3b = 18
Subtract both sides: 3b = 18-105
Simplify: 3b = -87
Divide: b = -29

Plug back into the first: a=21+b
a = 21 - 29
a = -8

Option D

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The length of human pregnancies from conception to birth varies according to an approximately normal distribution with a mean of
Varvara68 [4.7K]

Answer:

A) 68.33%

B) (234, 298)

Step-by-step explanation:

We have that the mean is 266 days (m) and the standard deviation is 16 days (sd), so we are asked:

A. P (250 x < 282)

P ((x1 - m) / sd < x < (x2 - m) / sd)

P ((250 - 266) / 16 < x < (282 - 266) / 16)

P (- 1 < z < 1)

P (z < 1) - P (-1 < z)

If we look in the normal distribution table we have to:

P (-1 < z) = 0.1587

P (z < 1) = 0.8413

replacing

0.8413 - 0.1587 = 0.6833

The percentage of pregnancies last between 250 and 282 days is 68.33%

B. We apply the experimental formula of 68-95-99.7

For middle 95% it is:

(m - 2 * sd, m + 2 * sd)

Thus,

m - 2 * sd <x <m + 2 * sd

we replace

266 - 2 * 16 <x <266 + 2 * 16

234 <x <298

That is, the interval would be (234, 298)

6 0
3 years ago
Can someone answer this please<br> Questions 19 and 21
Olegator [25]

Answer:

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Another very old approach to measure wind speed is through the use of a pressure tube

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The Richter scale is used to determine the intensity of earthquakes

Step-by-step explanation:

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2 years ago
I need help with this page. I don't get it.
yanalaym [24]
Which questions? im confused
7 0
3 years ago
35 POINTS
dmitriy555 [2]
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Answer:

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Step-by-step explanation:

I did it on a test too

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