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Novay_Z [31]
3 years ago
7

A farmer pumps water from an irrigation well to water his field. the time it takes to water the field varies inversely with the

rate at which the pump operates. it takes 20 hours to water the field when the pumping rate is 600 gallons per minute. if he adjusts the pump so that it pumps at a rate of 400 gallons per minute, how long will it take to water the field?
Mathematics
1 answer:
Mila [183]3 years ago
8 0
In order to answer this question, we use the concept of ratio and proportion wherein we use the equation,
                                 R1 / T2 = R2 / T1
where R is for rate and T is for time. Substituting the known values to the equation,
                                 (600)/x = (400)/ 20
The value of x from the equation is 30. Thus, it will take 30 hours if the rate was adjusted to 400 gallons per minute. 
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If a^(b/4) = 16 for positive integers a and b, what is one possible value of b?.
Verizon [17]

Answer:

Step-by-step explanation:

a^{(\dfrac{b}{4})} = 16\\\\\\Both \ sides \ raise \ to \ 4\\\\(a^{\dfrac{b}{4}})^{4} = 16^{4}\\\\a^{\dfrac{b}{4}*4}=16^{4}\\\\a^{b}=16^{4}

b = 4

5 0
2 years ago
What is 345.5 plus three tenths ?
vekshin1

Answer:

345.8

Step-by-step explanation:

7 0
3 years ago
One side of a triangle is 3 times the second side. The third side is 17 feet longer than the second side. The perimeter of a
Nadya [2.5K]

Answer:

Step-by-step explanation:

lets have one side =a

P=3a+a+(17+a)=52

P=5a+17=52

5a=52-17

5a=35

a=7

second side=21

third side=24

3 0
3 years ago
if f(1) = -5 and f(n) = f(n-1) +7, find the first four terms and the common difference of the sequence
Alex_Xolod [135]

Answer:

- 5, 2, 9, 16 and d = + 7

Step-by-step explanation:

to obtain the first four terms substitute n = 2, 3, 4 into the recursive formula

f(1) = - 5 ← given

f(2) = f(1) + 7 = - 5 + 7 = 2

f(3) = f(2) + 7 = 2 + 7 = 9

f(4) = f(3) + 7 = 9 + 7 = 16

common difference d = 16 - 9 = 9 - 2 = 2 - (- 5) = 7



6 0
2 years ago
Suppose that W1, W2, and W3 are independent uniform random variables with the following distributions: Wi ~ Uni(0,10*i). What is
nadya68 [22]

I'll leave the computation via R to you. The W_i are distributed uniformly on the intervals [0,10i], so that

f_{W_i}(w)=\begin{cases}\dfrac1{10i}&\text{for }0\le w\le10i\\\\0&\text{otherwise}\end{cases}

each with mean/expectation

E[W_i]=\displaystyle\int_{-\infty}^\infty wf_{W_i}(w)\,\mathrm dw=\int_0^{10i}\frac w{10i}\,\mathrm dw=5i

and variance

\mathrm{Var}[W_i]=E[(W_i-E[W_i])^2]=E[{W_i}^2]-E[W_i]^2

We have

E[{W_i}^2]=\displaystyle\int_{-\infty}^\infty w^2f_{W_i}(w)\,\mathrm dw=\int_0^{10i}\frac{w^2}{10i}\,\mathrm dw=\frac{100i^2}3

so that

\mathrm{Var}[W_i]=\dfrac{25i^2}3

Now,

E[W_1+W_2+W_3]=E[W_1]+E[W_2]+E[W_3]=5+10+15=30

and

\mathrm{Var}[W_1+W_2+W_3]=E\left[\big((W_1+W_2+W_3)-E[W_1+W_2+W_3]\big)^2\right]

\mathrm{Var}[W_1+W_2+W_3]=E[(W_1+W_2+W_3)^2]-E[W_1+W_2+W_3]^2

We have

(W_1+W_2+W_3)^2={W_1}^2+{W_2}^2+{W_3}^2+2(W_1W_2+W_1W_3+W_2W_3)

E[(W_1+W_2+W_3)^2]

=E[{W_1}^2]+E[{W_2}^2]+E[{W_3}^2]+2(E[W_1]E[W_2]+E[W_1]E[W_3]+E[W_2]E[W_3])

because W_i and W_j are independent when i\neq j, and so

E[(W_1+W_2+W_3)^2]=\dfrac{100}3+\dfrac{400}3+300+2(50+75+150)=\dfrac{3050}3

giving a variance of

\mathrm{Var}[W_1+W_2+W_3]=\dfrac{3050}3-30^2=\dfrac{350}3

and so the standard deviation is \sqrt{\dfrac{350}3}\approx\boxed{116.67}

# # #

A faster way, assuming you know the variance of a linear combination of independent random variables, is to compute

\mathrm{Var}[W_1+W_2+W_3]

=\mathrm{Var}[W_1]+\mathrm{Var}[W_2]+\mathrm{Var}[W_3]+2(\mathrm{Cov}[W_1,W_2]+\mathrm{Cov}[W_1,W_3]+\mathrm{Cov}[W_2,W_3])

and since the W_i are independent, each covariance is 0. Then

\mathrm{Var}[W_1+W_2+W_3]=\mathrm{Var}[W_1]+\mathrm{Var}[W_2]+\mathrm{Var}[W_3]

\mathrm{Var}[W_1+W_2+W_3]=\dfrac{25}3+\dfrac{100}3+75=\dfrac{350}3

and take the square root to get the standard deviation.

8 0
3 years ago
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