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FromTheMoon [43]
3 years ago
12

65 POINTS!!! Amy works at the Apple Store at a commission rate of 3%. Ipads are 18% off on Mac Mondays. She helps a customer who

buys, 2 Ipads originally priced at $499, and an iPhone priced at $575. If all purchases are made on Mac Monday and the sales tax rate is 8.875 What is the total amount the customer will pay?
Students answer- $575 + 499 + 499 = 1573 times 1.0875 = $1710.64

Identify the students mistake in the given answer. Then explain why the answer is incorrect and give the correct way to do it.
Mathematics
1 answer:
klio [65]3 years ago
5 0

Answer:

  1. The first mistake was in not taking 18% off the iPad price. A second mistake was in using an incorrect value for the sales tax multiplier. Those two mistakes together are why the answer is incorrect.
  2. ($575 +0.82·2·499)·1.08875 = $1517.02

Step-by-step explanation:

iPads are 18% off on the day of purchase, so they should be charged at ...

   100% -18% = 82%

of full price. The sum shown includes two iPads at $499 each, without any discount. The total price is too high by $179.64.

The tax rate is given as 8.875%, so the multiplier on price will be ...

  100% +8.875% = 108.875% = 1.08875

The multiplier used by the student in the problem is 1.0875, so is too low.

_____

A correct computation could be written as ...

  ($575 + 2×499×0.82)×1.08875 ≈ $1517.02

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rusak2 [61]

Answer:

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Step-by-step explanation:

8 0
3 years ago
A recent kellogg survey shows that approximately 34% of americans eat breakfast. suppose alex takes a random sample of four amer
vlabodo [156]

This kind of experiments are ruled by Bernoulli's formula. If you have probability p of "success", and you want k successes in n trials, the probability is


\binom{n}{k}p^k(1-p)^{n-k}


It's easier to compute the first probability by difference: instead of computing the probability of the event "at least one of the surveyed eats breakfast", let's compute the probability of its contrary: none of them eats breakfast. So, we want 0 successes in 4 trials, with probability of success 0.34. The formula yields


\binom{4}{0} 0.34^0 0.64^4 = 0.64^4 \approx 0.17 = 17\%


Since the contrary has probability 17%, our event "at least one of the surveyed eats breakfast" has probability 83%.


As for the second question, the event "at least three of the surveyed eats breakfast" is the union of the events "exactly three of the surveyed eats breakfast" and "exactly four of the surveyed eats breakfast". So, we just need to sum their probabilities:


\binom{4}{3} 0.34^3 0.64^1 +\binom{4}{4} 0.34^4 0.64^0 = 4\cdot  0.34^3 0.64 + 0.34^4 \approx 0.11 = 11\%

3 0
3 years ago
A common assumption in modeling drug assimilation is that the blood volume in a person is a single compartment that behaves like
mixas84 [53]

Answer:

a) \mathbf{\dfrac{dx}{dt} = 30 - 0.015 x}

b) \mathbf{x = 2000 - 2000e^{-0.015t}}

c)  the  steady state mass of the drug is 2000 mg

d) t ≅ 153.51  minutes

Step-by-step explanation:

From the given information;

At time t= 0

an intravenous line is inserted into a vein (into the tank) that carries a drug solution with a concentration of 500

The inflow rate is 0.06 L/min.

Assume the drug is quickly mixed thoroughly in the blood and that the volume of blood remains constant.

The objective of the question is to calculate the following :

a) Write an initial value problem that models the mass of the drug in the blood for t ≥ 0.

From above information given :

Rate _{(in)}= 500 \ mg/L  \times 0.06 \  L/min = 30 mg/min

Rate _{(out)}=\dfrac{x}{4} \ mg/L  \times 0.06 \  L/min = 0.015x \  mg/min

Therefore;

\dfrac{dx}{dt} = Rate_{(in)} - Rate_{(out)}

with respect to  x(0) = 0

\mathbf{\dfrac{dx}{dt} = 30 - 0.015 x}

b) Solve the initial value problem and graph both the mass of the drug and the concentration of the drug.

\dfrac{dx}{dt} = -0.015(x - 2000)

\dfrac{dx}{(x - 2000)} = -0.015 \times dt

By Using Integration Method:

ln(x - 2000) = -0.015t + C

x -2000 = Ce^{(-0.015t)

x = 2000 + Ce^{(-0.015t)}

However; if x(0) = 0 ;

Then

C = -2000

Therefore

\mathbf{x = 2000 - 2000e^{-0.015t}}

c) What is the steady-state mass of the drug in the blood?

the steady-state mass of the drug in the blood when t = infinity

\mathbf{x = 2000 - 2000e^{-0.015 \times \infty }}

x = 2000 - 0

x = 2000

Thus; the  steady state mass of the drug is 2000 mg

d) After how many minutes does the drug mass reach 90% of its stead-state level?

After 90% of its steady state level; the mas of the drug is 90% × 2000

= 0.9 × 2000

= 1800

Hence;

\mathbf{1800 = 2000 - 2000e^{(-0.015t)}}

0.1 = e^{(-0.015t)

ln(0.1) = -0.015t

t = -\dfrac{In(0.1)}{0.015}

t = 153.5056729

t ≅ 153.51  minutes

4 0
3 years ago
Eliza Savage received a statement from her bank showing a checking account balance of $324.18 as of January 18. Her own checkboo
Svetlanka [38]
January 18th $324.18
January 29th $487.38

$487.38 - $324.18 = $163.20

8 0
4 years ago
The flash of lightning travels at the speed of light, which is about 186,000 miles per second. The sound of lightning (thunder)
4vir4ik [10]

Answer:

A.  <u>Distance of the lightning after 4 seconds = 744,000 miles</u>

<u>B. Distance of the lightning after n seconds = 186,000 * n</u>

Step-by-step explanation:

1. Let's review the information given to us to answer the question correctly:

Speed of lightning = 186,000 miles per second

Speed of sound = 750 miles per hour

2. A.  If you see a flash of lightning, then hear the thunder 4 seconds later, how far away is the lightning?

Distance of the lightning after 4 seconds = 186,000 * 4

<u>Distance of the lightning after 4 seconds = 744,000 miles</u>

<u>B. Now let’s generalize that result. Suppose it takes n seconds to hear the thunder after a flash of lightning. How far away is the lightning, in terms of n?</u>

<u>Distance of the lightning after n seconds = 186,000 * n</u>

4 0
3 years ago
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