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3 years ago

What percent of the first 20 natural numbers are prime numbers?

Mathematics

2 answers:

BARSIC [14]3 years ago

6 0

Answer: The required percentage is 40%.

Step-by-step explanation: We are given to find the percentage of the first 20 natural numbers that are prime.

We know that

first 20 natural numbers are 1, 2, 3, 4, . . . , 19, 20.

And, the prime numbers among them are 2, 3, 5, 7, 11, 13, 17 and 19.

So, if S be the sample space for the experiment and A be the event of selecting a prime number.

Then, we have

n(S) = 20 and n(A) = 8.

Therefore, the probability of event A is given by

$P(A)=\dfrac{n(A)}{n(S)}=\dfrac{8}{20}=\dfrac{2}{5}\times100\%=40\%.$

Thus, the required percentage is 40%.

Brilliant_brown [7]3 years ago

3 0

The primes are 2, 3, 5, 7, 11, 13, 17, 19. There are 8 of them, so they make up 40% of the numbers 1–20.

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Please solve with explanation (high points)

Hunter-Best [27]

Step-by-step explanation:

so, we have a large triangle made of the 2 cables as legs and the ground distance AB as baseline.

the tower is the height to the baseline of that large triangle.

let's call the top of the tower T.

and remember, the sum of all angles in a triangle is always 180°.

we know the angle A = 62°, and angle B = 72°.

assuming that AB is a truly horizontal line that means that the 2 legs (cables) have different lengths, the triangle is not isoceles, and the tower is not in the middle of the baseline.

so, the height (tower) splits the baseline into 2 parts. let's call them p and q.

p + q = 12 m

p = 12 - q

let's simply define that p is the part of the baseline on the A side, and q is the part of the baseline on the B side.

we have now 2 small right-angled triangles the large height (tower) splits the large triangle into.

one has the sides

AT, height (tower), p

angle A = 62°

angle T = 180 - 90 - 62 = 28°

the other has the sides

BT, height (tower), q

angle B = 72°

angle T = 180 - 90 - 72 = 18°

now remember the law of sine :

a/sin(A) = b/sin(B) = c/sin(C)

with the sides and the associated angles being opposite.

p/sin(28) = height/sin(62)

q/sin(18) = height/sin(72)

we know from above that

p = 12 - q

so,

(12 - q)/sin(28) = height/sin(62)

height = (12 - q)×sin(62)/sin(28)

q/sin(18) = height/sin(72)

height = q×sin(72)/sin(18)

and therefore, as height = height we get

(12 - q)×sin(62)/sin(28) = q×sin(72)/sin(18)

(12 - q)×sin(62)×sin(18) = q×sin(72)×sin(28)

12×sin(62)×sin(18) - q×sin(62)×sin(18) =

= q×sin(72)×sin(28)

12×sin(62)×sin(18) = q×sin(72)×sin(28) + q×sin(62)×sin(18) =

= q×(sin(72)×sin(28) + sin(62)×sin(18))

q = 12×sin(62)×sin(18) / (sin(72)×sin(28) + sin(62)×sin(18))

q = 4.551603755... m

p = 12 - q = 7.448396245... m

height = q×sin(72)/sin(18) = 14.00839594... m ≈ 14 m

the cell tower is about 14 m tall.

7 0

2 years ago

This question has two parts. First answer Part A Then, answer Part 8

8_murik_8 [283]

Answer:

In part A first do addition of all 3 then add the no 6,2,3 then minus both the ans then you will find the final ans

6 0

2 years ago

Need some help with this question, any help is appreciated!

Xelga [282]

Answer:

The answer to your question is: third option is correct

Step-by-step explanation:

According to the graph we can see that the points where both lines crosses are:

A (4, 8) and B (-4, 0)

6 0

4 years ago

Please help and show how you got the answer:

kari74 [83]

4 - 6n = 60 - 2n subtract 4 from both sides

-6n = 56 - 2n add 2n to both sides

-4n = 56 divide both sides by (-4)

n = - 14

-7 + 11p = 3p - 47 add 7 to both sides

11p = 3p - 40 subtract 3p from both sides

8p = -40 divide both sides by 8

p = - 5

3a - 28 - 7a = 10a combine like terms

(3a - 7a) - 28 = 10a

-4a - 28 = 10a add 28 to both sides

-4a = 10a + 28 subtract 10 from both sides

-14a = 28 divide both sides by (-14)

a = - 2

17 - 5r + 9r = 12 + 6r - 1 combine like terms

17 + (-5r + 9r) = (12 - 1) + 6r

17 + 4r = 11 + 6r subtract 17 from both sides

4r = -6 + 6r subtract 6r from both sides

-2r = -6 divide both sides by (-2)

r = 3

8(y - 7) = -2(y + 3) use distributive property: a(b + c) = ab + ac

(8)(y) + (8)(-7) = (-2)(y) + (-2)(3)

8y - 56 = -2y - 6 add 56 to both sides

8y = -2y + 50 add 2y to both sides

10y = 50 divide both sides by 10

y = 5

-3(8k + 5) = 3(9 - k) use distributive property: a(b + c) = ab + ac

(-3)(8k) + (-3)(5) = (3)(9) + (3)(-k)

-24k - 15 = 27 - 3k add 15 to both sides

-24k = 42 - 3k add 3k to both sides

-21k = 42 divide both sides by (-21)

k = -2

2(3v - 5) = 2(v - 11) - 4 use distributive property: a(b + c) = ab + ac

(2)(3v) + (2)(-5) = (2)(v) + (2)(-11) - 4

6v - 10 = 2v - 22 - 4

6v - 10 = 2v - 26 add 10 to both sides

6v = 2v - 16 subtract 2v from both sides

4v = -16 divide both sides by 4

v = -4

-2/3 (15x + 3) -3x - 9 use distributive property: a(b + c) = ab + ac

= (-2/3)(15x) + (-2/3)(3) - 3x - 9

= (-2)(5x) - 2 - 3x - 9

= -10x - 2 - 3x - 9 combine like terms

= (-10x - 3x) + (-2 - 9)

= -13x - 11

3(1 - 9a) + 22a = 2(2a - 9) - 15

use distributive property: a(b + c) = ab + ac

(3)(1) + (3)(-9a) + 22a = (2)(2a) + (2)(-9) - 15

3 - 27a + 22a = 4a - 18 - 15 combine like terms

3 + (-27a + 22a) = 4a + (-18 - 15)

3 - 5a = 4a - 33 subtract 3 from both sides

-5a = 4a - 36 subtract 4a from both sides

-9a = -36 divide both sides by (-9)

a = 4

-3(3m - 10) - 7 = -5(m + 1) + 3m

use distributive property: a(b + c) = ab + ac

(-3)(3m) + (-3)(-10) - 7 = (-5)(m) + (-5)(1) + 3m

-9m + 30 - 7 = -5m - 5 + 3m combine like terms

-9m + (30 - 7) = (-5m + 3m) - 5

-9m + 23 = -2m - 5 subtract 23 from both sides

-9m = -2m - 28 add 2m to both sides

-7m = -28 divide both sides by (-7)

m = 4

6 0

3 years ago

Twenty percent of what number is 5?

Semenov [28]

Answer:

A. 25

Step-by-step explanation:

25 split into 5 groups, 5 in each of them.

There are 5 20's in 100 (the total)

25 = 5 + 5 + 5 + 5 + 5

I hope the explanation makes sense!

7 0

3 years ago