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2 years ago

Answer the following and provide if the answer is negative or positive.

Mathematics

2 answers:

Bumek [7]2 years ago

6 0

Answer:

(+) x (+) x (-) = -

(+) x (-) x (+) =-

(-) x (-) = +

(+) x (+) x (+) = +

(-) x (-) x (-) x (-) =+

const2013 [10]2 years ago

4 0

(+) x (+) x (-) =(-)

(+) x (-) x (+) =(-)

(-) x (-) =(+)

(+) x (+) x (+) = (+)

(-) x (-) x (-) x (-) =(+)

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A tank contains 60 kg of salt and 1000 L of water. Pure water enters a tank at the rate 6 L/min. The solution is mixed and drain

MissTica

Answer:

(a) 60 kg; (b) 21.6 kg; (c) 0 kg/L

Step-by-step explanation:

(a) Initial amount of salt in tank

The tank initially contains 60 kg of salt.

(b) Amount of salt after 4.5 h

$\text{Let A = mass of salt after t min}\\\text{and }r_{i} = \text{rate of salt coming into tank}\\\text{and }r_{0} =\text{rate of salt going out of tank}$

(i) Set up an expression for the rate of change of salt concentration.

$\dfrac{\text{d}A}{\text{d}t} = r_{i} - r_{o}\\\\\text{The fresh water is entering with no salt, so}\\ r_{i} = 0\\r_{o} = \dfrac{\text{3 L}}{\text{1 min}} \times \dfrac {A\text{ kg}}{\text{1000 L}} =\dfrac{3A}{1000}\text{ kg/min}\\\\\dfrac{\text{d}A}{\text{d}t} = -0.003A \text{ kg/min}$

(ii) Integrate the expression

$\dfrac{\text{d}A}{\text{d}t} = -0.003A\\\\\dfrac{\text{d}A}{A} = -0.003\text{d}t\\\\\int \dfrac{\text{d}A}{A} = -\int 0.003\text{d}t\\\\\ln A = -0.003t + C$

(iii) Find the constant of integration

$\ln A = -0.003t + C\\\text{At t = 0, A = 60 kg/1000 L = 0.060 kg/L} \\\ln (0.060) = -0.003\times0 + C\\C = \ln(0.060)$

(iv) Solve for A as a function of time.

$\text{The integrated rate expression is}\\\ln A = -0.003t + \ln(0.060)\\\text{Solve for } A\\A = 0.060e^{-0.003t}$

(v) Calculate the amount of salt after 4.5 h

a. Convert hours to minutes

$\text{Time} = \text{4.5 h} \times \dfrac{\text{60 min}}{\text{1h}} = \text{270 min}$

b.Calculate the concentration

$A = 0.060e^{-0.003t} = 0.060e^{-0.003\times270} = 0.060e^{-0.81} = 0.060 \times 0.445 = \text{0.0267 kg/L}$

c. Calculate the volume

The tank has been filling at 6 L/min and draining at 3 L/min, so it is filling at a net rate of 3 L/min.

The volume added in 4.5 h is

$\text{Volume added} = \text{270 min} \times \dfrac{\text{3 L}}{\text{1 min}} = \text{810 L}$

Total volume in tank = 1000 L + 810 L = 1810 L

d. Calculate the mass of salt in the tank

$\text{Mass of salt in tank } = \text{1810 L} \times \dfrac{\text{0.0267 kg}}{\text{1 L}} = \textbf{21.6 kg}$

(c) Concentration at infinite time

$\text{As t $\longrightarrow \, -\infty,\, e^{-\infty} \longrightarrow \, 0$, so A $\longrightarrow \, 0$.}$

This makes sense, because the salt is continuously being flushed out by the fresh water coming in.

The graph below shows how the concentration of salt varies with time.

3 0

2 years ago

44 x 4 help now pls help

djyliett [7]

176 is the answer hope i helped!

6 0

3 years ago

Read 2 more answers

the tickets for a dance recital cost $5.00 for adults and $2.00 for children. if the total number of tickets sold was 295 and th

alukav5142 [94]

210 adult tickets
85 children tickets
210 x $5 = $1,050
85 x $2 = $170
1,050 + 170 =1,220

8 0

2 years ago

If the order of three loci is A B C, and the map distance between A and B is 15 m.u., and the map distance between B and C is 20

zysi [14]

Answer:

Therefore, we conclute that the map distance between A and C is 35 m.u..

Step-by-step explanation:

We know that the order of three loci is A B C, and the map distance between A and B is 15 m.u., and the map distance between B and C is 20 m.u. We calculate the map distance between A and C.

Therefore, we get

$AC=AB+BC\\\\AC=15+20\\\\AC=35\\$

Therefore, we conclute that the map distance between A and C is 35 m.u..

4 0

2 years ago

Which number line shows 2 + (-5)?

ladessa [460]

Answer:

-3

Step-by-step explanation:

2+(-5)

2-5=-3

that is you solve the equation and trace it on the number line

7 0

2 years ago