Find the area of a circle with radius 18 in

Amazon was valued at 430 billion dollars. Write this number in scientific notation

pshichka [43]

Answer:

430 billion (430,000,000,000) is 4.3 x 10^11 in scientific notation

3 0

4 years ago

The sum of first three terms of a finite geometric series is -7/10 and their product is -1/125. [Hint: Use a/r, a, and ar to rep

Alchen [17]

Ooh, fun

geometric sequences can be represented as
$a_n=a(r)^{n-1}$
so the first 3 terms are
$a_1=a$
$a_2=a(r)$
$a_2=a(r)^2$

the sum is -7/10
$\frac{-7}{10}=a+ar+ar^2$
and their product is -1/125
$\frac{-1}{125}=(a)(ar)(ar^2)=a^3r^3=(ar)^3$

from the 2nd equation we can take the cube root of both sides to get
$\frac{-1}{5}=ar$
note that a=ar/r and ar²=(ar)r
so now rewrite 1st equation as
$\frac{-7}{10}=\frac{ar}{r}+ar+(ar)r$
subsituting -1/5 for ar
$\frac{-7}{10}=\frac{\frac{-1}{5}}{r}+\frac{-1}{5}+(\frac{-1}{5})r$
which simplifies to
$\frac{-7}{10}=\frac{-1}{5r}+\frac{-1}{5}+\frac{-r}{5}$
multiply both sides by 10r
-7r=-2-2r-2r²
add (2r²+2r+2) to both sides
2r²-5r+2=0
solve using quadratic formula
for $ax^2+bx+c=0$
$x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}$
so
for 2r²-5r+2=0
a=2
b=-5
c=2

$r=\frac{-(-5) \pm \sqrt{(-5)^2-4(2)(2)}}{2(2)}$
$r=\frac{5 \pm \sqrt{25-16}}{4}$
$r=\frac{5 \pm \sqrt{9}}{4}$
$r=\frac{5 \pm 3}{4}$
so
$r=\frac{5+3}{4}=\frac{8}{4}=2$ or $r=\frac{5-3}{4}=\frac{2}{4}=\frac{1}{2}$

use them to solve for the value of a
$\frac{-1}{5}=ar$
$\frac{-1}{5r}=a$
try for r=2 and 1/2
$a=\frac{-1}{10}$ or $a=\frac{-2}{5}$

test each
for a=-1/10 and r=2
a+ar+ar²= $\frac{-1}{10}+\frac{-2}{10}+\frac{-4}{10}=\frac{-7}{10}$
it works

for a=-2/5 and r=1/2
a+ar+ar²= $\frac{-2}{5}+\frac{-1}{5}+\frac{-1}{10}=\frac{-7}{10}$
it works

both have the same terms but one is simplified

the 3 numbers are $\frac{-2}{5}$ , $\frac{-1}{5}$ , and $\frac{-1}{10}$

6 0

3 years ago

I need help it says to use 3.14 PI

aliya0001 [1]

Answer:

Step-by-step explanation:

$\text{We have a rectangle of 100 by 50 and half a circle with a radius of 25.}\\ \\ A=100(50)+3.14(25^2)\\ \\ A\approx 6962.5\ m^2$

8 0

3 years ago

Anna gets paid $8.75/hour working as a barista at Coffee Break. Her boss pays her $9.00/hour for creating the weekly advertiseme

vladimir1956 [14]

Answer:

i believe it would be $443.75

Step-by-step explanation:

just add 8.75 to 9.00 then multiply it by 25

8.75+9.00= 17.75 x 25= 443.75

if its a different type of equation then maybe this didn't help but i hope it does

7 0

4 years ago

A survey was conducted to measure the height of men. In the survey, respondents were grouped by age. In the 20-29 group the grou

kotykmax [81]

Answer:

(a) The probability that his height is less than 66 inches is 0.2743.

(b) The probability that the height is between 66 and 71 inches is 0.4679.

(c) The probability that the height is more than 71 inches is 0.2578.

Step-by-step explanation:

The data given in the question is:

Mean (μ) = 68.4

Standard Deviation (σ) = 4

Let X denote the height of men. We will use the normal distribution z-score formula to calculate the z-score and then look up the probability in the normal probability distribution table. The z-score formula is:

z = (X - μ)/σ

(a) For P(X<66), first calculate the z value.

z = (66-68.4)/4

z = -0.6 (Look up this value in the standard normal distribution table)

P(z<-0.6) = 0.2743

The probability that his height is less than 66 inches is 0.2743.

(b) P(66<X<71) = P(X<71) - P(X<66)

We need to find P(X<71) so, calculating the z-value:

z = (71-68.4)/4

z = 0.65

P(z<0.65) = 0.7422

P(66<X<71) = 0.7422 - 0.2743

P(66<X<71) = 0.4679

The probability that the height is between 66 and 71 inches is 0.4679.

(c) To find the probability P(X>71), we need to find P(X<71) and then subtract it from 1 because the normal distribution table gives values for P(X<k). We have already calculated the value of P(X<71) in part (b) so,

P(X>71) = 1 - P(X<71)

= 1 - 0.7422

P(X>71) = 0.2578

The probability that the height is more than 71 inches is 0.2578.

3 0

3 years ago