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3 years ago

A rectangle is shown below.

Mathematics

1 answer:

Dahasolnce [82]3 years ago

7 0

Answer:

a) 247.25 cm²

b) 62.0 cm

Step-by-step explanation:

All of these upper-bound/lower-bound problems are worked the same way. The bounds on the measurement are presumed to be half of one unit of the least-significant digit.

Here, the least significant digit of both numbers is in the "units" place, so the maximum error is presumed to be 1/2 unit, or ±0.5 cm.

If the measurement were 7.36 inches, the least significant digit is in the hundredths place, so the maximum error is presumed to be half a hundredth, or ±0.5 × 0.01 inches = ±0.005 inches.

To find the bounds on the measurement, you add or subtract this maximum error from the measurement. So, for the measurements in this problem, the maximum and minimum they can be are ...

21 cm: minimum of 21 - 0.5 = 20.5 cm; maximum of 21 + 0.5 = 21.5 cm

11 cm: minimum of 10.5 cm; maximum of 11.5 cm

If you wanted to express these as an inequality, you'd have to remember that half-units are rounded up, so the inequalities would be ...

20.5 cm ≤ long side < 21.5 cm

10.5 cm ≤ short side < 11.5 cm

a) The area is computed as the product of the rectangle's side length measurements. The area will be a maximum when both measurements are a maximum:

Amax = (21.5 cm)(11.5 cm)

Amax = 247.25 cm²

b) The perimeter is twice the sum of the lengths of two adjacent sides of the rectangle. The minimum perimeter will be the sum using the minimum side lengths, or ...

Pmin = 2(20.5 cm +10.5 cm) = 2(31.0 cm)

Pmin = 62.0 cm

_____

Comment on measurement bounds

You have to remember that these concepts are mathematical in nature, so only an approximation of the real world. If you have ever used a tape measure to measure a distance of any length, you will have discovered a couple of things:

different tape measures are different lengths
the measurement you make depends on how tight you stretch the tape (and often, on temperature and/or humidity)
it is amazingly hard to choose the "nearest" measurement when the value is halfway between marks on the tape. (That is, there is some fuzziness in the boundary between nearest units.)

So, mathematically, there will be very specific definitions and procedures to follow regarding measurement values. In the real world, you have to remember these are only an approximation to reality, hopefully a useful one.

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The chemistry class was making 300 gallons of 30% isopropyl alcohol. They mixed 12% with 42%. How much of each did they use?

alexgriva [62]

Answer:

The chemistry class mixed 120 gallons of 12% isopropyl alcohol and 180 gallons of 42% isopropyl alcohol.

Step-by-step explanation:

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

Amount of isopropyl alcohol made by the chemistry class = 300 of 30%

Amount of 12% isopropyl alcohol mixed by the chemistry class = x

Amount of 42% isopropyl alcohol mixed by the chemistry class = 300 - x

2. How much of each did they use?

Let's write our equation to solve for x, this way:

30% = 0.3, 12% = 0.12, 42% = 0.42

0.12x + 0.42 (300 - x) = 0.3 * 300

0.12x + 126 - 0.42x = 90

-0.3x = 90 - 126

-0.3x = -36

x = -36/-0.3

x = 120 ⇒ 300 - x = 180

Let's prove x = 120 is correct

0.12x + 0.42 (300 - x) = 0.3 * 300

0.12 * 120 + 0.42 (300 - 120) = 0.3 * 300

14.4 + 75.6 = 90

90 = 90

We proved x = 120 is correct

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3 years ago

Which expression is equivalent to -2 - 7?

SOVA2 [1]

Answer: -2 - (-7)

Step-by-step explanation: They both have the same outcome, 5. Which one is negative and one is positive. The last option is correct.

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3 years ago

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An alarming number of U.S. adults are either overweight or obese. The distinction between overweight and obese is made on the ba

madreJ [45]

Answer:

(A) The probability that a randomly selected adult is either overweight or obese is 0.688.

(B) The probability that a randomly selected adult is neither overweight nor obese is 0.312.

(D) The events "overweight" and "obese" mutually exclusive.

Step-by-step explanation:

Denote the events as follows:

X = a person is overweight

Y = a person is obese.

The information provided is:

A person is overweight if they have BMI 25 or more but below 30.

A person is obese if they have BMI 30 or more.

P (X) = 0.331

P (Y) = 0.357

(A)

The events of a person being overweight or obese cannot occur together.

Since if a person is overweight they have (25 ≤ BMI < 30) and if they are obese they have BMI ≥ 30.

So, P (X ∩ Y) = 0.

Compute the probability that a randomly selected adult is either overweight or obese as follows:

$P(X\cup Y)=P(X)+P(Y)-P(X\cap Y)\\=0.331+0.357-0\\=0.688$

Thus, the probability that a randomly selected adult is either overweight or obese is 0.688.

(B)

Commute the probability that a randomly selected adult is neither overweight nor obese as follows:

$P(X^{c}\cup Y^{c})=1-P(X\cup Y)\\=1-0.688\\=0.312$

Thus, the probability that a randomly selected adult is neither overweight nor obese is 0.312.

(C)

If two events cannot occur together, but they form a sample space when combined are known as exhaustive events.

For example, flip of coin. On a flip of a coin, the flip turns as either Heads or Tails but never both. But together the event of getting a Heads and Tails form a sample space of a single flip of a coin.

In this case also, together the event of a person being overweight or obese forms a sample space of people who are heavier in general.

Thus, the events "overweight" and "obese" exhaustive.

(D)

Mutually exclusive events are those events that cannot occur at the same time.

The events of a person being overweight and obese are mutually exclusive.

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2 years ago

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yulyashka [42]

Answer:

i√19

Step-by-step explanation:

Because √(-19) = √(-1)√19, and because √(-1) = i, we get i√19

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