Which is larger 589.1 or 58.91

$\bf \cfrac{2}{3}\cdot \cfrac{same}{same}\implies \stackrel{equivalent~fraction}{\cfrac{2(same)}{3(same)}}\qquad therefore\qquad \cfrac{2}{3}\cdot \cfrac{9}{9}\implies \stackrel{equivalent}{\cfrac{18}{27}}$

3 0

3 years ago

A tank initially contains 60 gallons of brine, with 30 pounds of salt in solution. Pure water runs into the tank at 3 gallons pe

adoni [48]

Answer:

the amount of time until 23 pounds of salt remain in the tank is 0.088 minutes.

Step-by-step explanation:

The variation of the concentration of salt can be expressed as:

$\frac{dC}{dt}=Ci*Qi-Co*Qo$

being

C1: the concentration of salt in the inflow

Qi: the flow entering the tank

C2: the concentration leaving the tank (the same concentration that is in every part of the tank at that moment)

Qo: the flow going out of the tank.

With no salt in the inflow (C1=0), the equation can be reduced to

$\frac{dC}{dt}=-Co*Qo$

Rearranging the equation, it becomes

$\frac{dC}{C}=-Qo*dt$

Integrating both sides

$\int\frac{dC}{C}=\int-Qo*dt\\ln(\abs{C})+x1=-Qo*t+x2\\ln(\abs{C})=-Qo*t+x\\C=exp^{-Qo*t+x}$

It is known that the concentration at t=0 is 30 pounds in 60 gallons, so C(0) is 0.5 pounds/gallon.

$C(0)=exp^{-Qo*0+x}=0.5\\exp^{x} =0.5\\x=ln(0.5)=-0.693\\$

The final equation for the concentration of salt at any given time is

$C=exp^{-3*t-0.693}$

To answer how long it will be until there are 23 pounds of salt in the tank, we can use the last equation:

$C=exp^{-3*t-0.693}\\(23/60)=exp^{-3*t-0.693}\\ln(23/60)=-3*t-0.693\\t=-\frac{ln(23/60)+0.693}{3}=-\frac{-0.959+0.693}{3}= -\frac{-0.266}{3}=0.088$

5 0

2 years ago

PLEASE PLEASE PLEASE PLEASE PLEASE PLEASE HELP ME!!!!!!!! THATS ALL. I WILL GIVE POINTS, FAN, MEDAL. PLEASE, I AM SO BAD AT MATH

aleksandrvk [35]

"measures to the nearest tenth of a pound" tell us to round each of the weights listed to the nearest tenth (since the unit is already pounds, no conversion is needed). What this means is if the second number to the right of the decimal is 5 or greater, then we add 1 to the first number to the right of the decimal (and replace the second number with a zero). With all this said, it's much easier to show you, rather than to try to explain it. :D

4.35 is rounded up to 4.4 because the second number to the right of the decimal is 5.
Packet A = 4.4
Packet B = 4.4
Packet C = 4.5
Packed D = 4.4
The question is asking what the heaviest reading will be, so from the whole list above we pick the highest number which is 4.5 pounds. Notice how the answer is not Packet C, or 4.48 pounds, but 4.5 pounds. It is asking for the reading, not the packet, nor the weight. Hope this helps.

7 0

3 years ago

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