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4 years ago

Explain how estimation helps you to place the decimal point when multiplying 3.9 x 5.3 ?

2 answers:

3 0

Well the answer to that is 20.67.
Also, you can simply find this out by placing the decimal as you solve the problem, meaning as when you solve like this
3.9
x5.3
--------
.
Drag the decimal down.

Nimfa-mama [501]4 years ago

3 0

If you round 3.9 to 4 and 5.3 to 5 you can easily multiply those numbers together and get 15.

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a survey amony freshman at a certain university revealed that the number of hours spent studying the week before final exams was

Marat540 [252]

Answer:

Probability that the average time spent studying for the sample was between 29 and 30 hours studying is 0.0321.

Step-by-step explanation:

We are given that the number of hours spent studying the week before final exams was normally distributed with mean 25 and standard deviation 15.

A sample of 36 students was selected.

Let $\bar X$ = sample average time spent studying

The z-score probability distribution for sample mean is given by;

Z = $\frac{ \bar X-\mu}{\frac{\sigma}{\sqrt{n} } }} }$ ~ N(0,1)

where, $\mu$ = population mean hours spent studying = 25 hours

$\sigma$ = standard deviation = 15 hours

n = sample of students = 36

The Z-score measures how many standard deviations the measure is away from the mean. After finding the Z-score, we look at the z-score table and find the p-value (area) associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X.

Now, Probability that the average time spent studying for the sample was between 29 and 30 hours studying is given by = P(29 hours < $\bar X$ < 30 hours)

P(29 hours < $\bar X$ < 30 hours) = P( $\bar X$ < 30 hours) - P( $\bar X$ $\leq$ 29 hours)

P( $\bar X$ < 30 hours) = P( $\frac{ \bar X-\mu}{\frac{\sigma}{\sqrt{n} } }} }$ < $\frac{ 30-25}{\frac{15}{\sqrt{36} } }} }$ ) = P(Z < 2) = 0.97725

P( $\bar X$ $\leq$ 29 hours) = P( $\frac{ \bar X-\mu}{\frac{\sigma}{\sqrt{n} } }} }$ $\leq$ $\frac{ 29-25}{\frac{15}{\sqrt{36} } }} }$ ) = P(Z $\leq$ 1.60) = 0.94520

So, in the z table the P(Z $\leq$ x) or P(Z < x) is given. So, the above probability is calculated by looking at the value of x = 2 and x = 1.60 in the z table which has an area of 0.97725 and 0.94520 respectively.

Therefore, P(29 hours < $\bar X$ < 30 hours) = 0.97725 - 0.94520 = 0.0321

Hence, the probability that the average time spent studying for the sample was between 29 and 30 hours studying is 0.0321.

7 0

3 years ago

A fuel tank has a volume of 36 gallons. When filled with biodiesel, it provides 4,500,000 BTUs. How many BTUs does 1 gallon of b

Tamiku [17]

Answer: 125,000 BTUs

Step-by-step explanation:

Hi, to answer this question we have to apply proportions:

A fuel tank has a volume of 36 gallons. When filled with biodiesel, it provides 4,500,000 BTUs

So, the proportion is:

36 gallons / 4,500,000 BTUs

For 1 gallon

1 gallon / x BTUs

36/4,500,000 = 1/x

Solving for x:

x = 1 / (36/4,500,000)

x = 125,000 BTUs

Feel free to ask for more if needed or if you did not understand something.

4 0

3 years ago

<img src="https://tex.z-dn.net/?f=solve%20%5C%3A%20%20%5C%5C%20%20%5C%5C%20find%20%5C%3A%20the%20%5C%3A%20area%20%5C%3A%20of%20%

N76 [4]

Area = l ×b

$a = l \times b \\ a = 11 \times 9 \\ a = 99$

5 0

3 years ago

Samantha works at a nursery, where she pots plants. it takes her 1 1/2 hours to pot 12 plants.

nignag [31]

Answer:

She could plant 9 plants.

Step-by-step explanation:

1 1/2 hours = 90 minutes, so 12 plants per 90 minutes. Which would mean 6 plants per 45 minutes. So in between 45 and 90 minutes (1 hour), and in between 6 and 12 plants (9).

Sorry if you didn't understand, I'm bad at explaining.

4 0

3 years ago

Plz help i will mark brainliest

Stels [109]

Answer:

Step-by-step explanation:

5 0

3 years ago