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Serggg [28]
3 years ago
8

Leila received a $90 gift card for a coffee store. She used it in buying some coffee that cost $8.64 per pound. After buying the

coffee, she had $64.08 left on her card. How many pounds of coffee did she buy?
Mathematics
1 answer:
klasskru [66]3 years ago
3 0
She bought 5 pounds of coffee
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On a math quiz, Tina scored 5 less points than Ben. Juan scored
kumpel [21]

Answer:

a) t=b-5 b) j=b+3+2

Step-by-step explanation:

t is tina, we don't know how much Ben scored so we use b, then subtract 5 because tina got 5 less. same thing for Juan but we add the 3 points he got more than Ben and the 2 extra credit points

7 0
3 years ago
A 500-gallon tank initially contains 220 gallons of pure distilled water. Brine containing 5 pounds of salt per gallon flows int
Wittaler [7]

Answer: The amount of salt in the tank after 8 minutes is 36.52 pounds.

Step-by-step explanation:

Salt in the tank is modelled by the Principle of Mass Conservation, which states:

(Salt mass rate per unit time to the tank) - (Salt mass per unit time from the tank) = (Salt accumulation rate of the tank)

Flow is measured as the product of salt concentration and flow. A well stirred mixture means that salt concentrations within tank and in the output mass flow are the same. Inflow salt concentration remains constant. Hence:

c_{0} \cdot f_{in} - c(t) \cdot f_{out} = \frac{d(V_{tank}(t) \cdot c(t))}{dt}

By expanding the previous equation:

c_{0} \cdot f_{in} - c(t) \cdot f_{out} = V_{tank}(t) \cdot \frac{dc(t)}{dt} + \frac{dV_{tank}(t)}{dt} \cdot c(t)

The tank capacity and capacity rate of change given in gallons and gallons per minute are, respectivelly:

V_{tank} = 220\\\frac{dV_{tank}(t)}{dt} = 0

Since there is no accumulation within the tank, expression is simplified to this:

c_{0} \cdot f_{in} - c(t) \cdot f_{out} = V_{tank}(t) \cdot \frac{dc(t)}{dt}

By rearranging the expression, it is noticed the presence of a First-Order Non-Homogeneous Linear Ordinary Differential Equation:

V_{tank} \cdot \frac{dc(t)}{dt} + f_{out} \cdot c(t) = c_0 \cdot f_{in}, where c(0) = 0 \frac{pounds}{gallon}.

\frac{dc(t)}{dt} + \frac{f_{out}}{V_{tank}} \cdot c(t) = \frac{c_0}{V_{tank}} \cdot f_{in}

The solution of this equation is:

c(t) = \frac{c_{0}}{f_{out}} \cdot ({1-e^{-\frac{f_{out}}{V_{tank}}\cdot t }})

The salt concentration after 8 minutes is:

c(8) = 0.166 \frac{pounds}{gallon}

The instantaneous amount of salt in the tank is:

m_{salt} = (0.166 \frac{pounds}{gallon}) \cdot (220 gallons)\\m_{salt} = 36.52 pounds

3 0
3 years ago
This is for a friend, please help!
Deffense [45]

Answer:

x=-4-4√3

Step-by-step explanation:

3 0
3 years ago
The diameter of a circle is 8 inches. What is the area?
makkiz [27]

Answer:

16 × π in 2

Step-by-step explanation:

the formula to find the area of a triangle is πr^2, you are given the diameter which equals 2r. so split the diameter in half and plug your number in. π4^2

4^2=16

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8 0
3 years ago
Can 19/23 be simplified because my teacher said it can but I say I can not be simplified
mihalych1998 [28]
I agree with you you both of those are prime numbers so it cant be simplified
8 0
3 years ago
Read 2 more answers
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