X+2y=19 and x+y=13 in substitution methood

Raymond has 120 books on his bookshelf that he has not read. He plans on reading 3 books per week until there are only 24 books

Oksi-84 [34.3K]

Answer: The correct option is (A) $120-3w=24;~32.$

Step-by-step explanation: Given that Raymond has 120 books on his bookshelf that he has not read. He plans on reading 3 books per week until there are only 24 books that he still needs to read.

We are to find the equation that can be used to determine the number of weeks it will take Raymond to have only 24 books left.

Also, we are to find the number of weeks.

The number of weeks it will take Raymond to have only 24 books left is represented by 'w'.

We have

number of books read by Raymond is 1 week = 3.

So, number of books read by Raymond is w weeks = 3w.

Since, there are total 120 books on his bookshelf, so the number of books left to read after w weeks will be

$120-3w.$

According to the given information, we get

$120-3w=24\\\\\Rightarrow 3w=120-24\\\\\Rightarrow 3w=96\\\\\Rightarrow w=32.$

thus, the required equation is $120-3w=24$ and number of weeks is 32.

Option (A) is correct.

8 0

3 years ago

Plz explain it to me? and answer

Viefleur [7K]

The question states that both parts of Noshi's desk were shaped like trapezoids and both had a height of 3.

We know that the formula for area of a trapezoid is (a+b)/2 * h, where a and b are bases of the trapezoid and h is the height. Note: This is like any other form of trying to find the area, because we are doing base times height, however, we need to divide the sum of the bases by 2 to find the average base length.

Let's call the first trapezoid on the left Trapezoid A and the second slanted trapezoid Trapezoid B.

Area of Trapezoid A = (a+b)/2 * h = (5+8)/2 * 3 = 13/2 * 3 = 6.5 * 3 = 19.5 feet
Area of Trapezoid B = (a+b)/2 * h = (4+9)/2 * 3 = 13/2 * 3 = 6.5 * 3 = 19.5 feet

To find the area of Noshi's total desk, we simply need to add the areas of Trapezoid A and Trapezoid B together.

19.5 feet + 19.5 feet = 39 feet

Therefore, the area of Noshi's desk is 39 feet.

Hope this helps! :)

7 0

3 years ago

Suppose a geyser has a mean time between irruption’s of 75 minutes. If the interval of time between the eruption is normally dis

lesya [120]

Answer:

(a) The probability that a randomly selected Time interval between irruption is longer than 84 minutes is 0.3264.

(b) The probability that a random sample of 13 time intervals between irruption has a mean longer than 84 minutes is 0.0526.

(c) The probability that a random sample of 20 time intervals between irruption has a mean longer than 84 minutes is 0.0222.

(d) The probability decreases because the variability in the sample mean decreases as we increase the sample size

(e) The population mean may be larger than 75 minutes between irruption.

Step-by-step explanation:

We are given that a geyser has a mean time between irruption of 75 minutes. Also, the interval of time between the eruption is normally distributed with a standard deviation of 20 minutes.

(a) Let X = the interval of time between the eruption

So, X ~ Normal( $\mu=75, \sigma^{2} =20$ )

The z-score probability distribution for the normal distribution is given by;

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

where, $\mu$ = population mean time between irruption = 75 minutes

$\sigma$ = standard deviation = 20 minutes

Now, the probability that a randomly selected Time interval between irruption is longer than 84 minutes is given by = P(X > 84 min)

P(X > 84 min) = P( $\frac{X-\mu}{\sigma}$ > $\frac{84-75}{20}$ ) = P(Z > 0.45) = 1 - P(Z $\leq$ 0.45)

= 1 - 0.6736 = 0.3264

The above probability is calculated by looking at the value of x = 0.45 in the z table which has an area of 0.6736.

(b) Let $\bar X$ = sample time intervals between the eruption

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

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

where, $\mu$ = population mean time between irruption = 75 minutes

$\sigma$ = standard deviation = 20 minutes

n = sample of time intervals = 13

Now, the probability that a random sample of 13 time intervals between irruption has a mean longer than 84 minutes is given by = P( $\bar X$ > 84 min)

P( $\bar X$ > 84 min) = P( $\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }$ > $\frac{84-75}{\frac{20}{\sqrt{13} } }$ ) = P(Z > 1.62) = 1 - P(Z $\leq$ 1.62)

= 1 - 0.9474 = 0.0526

The above probability is calculated by looking at the value of x = 1.62 in the z table which has an area of 0.9474.

(c) Let $\bar X$ = sample time intervals between the eruption

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

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

where, $\mu$ = population mean time between irruption = 75 minutes

$\sigma$ = standard deviation = 20 minutes

n = sample of time intervals = 20

Now, the probability that a random sample of 20 time intervals between irruption has a mean longer than 84 minutes is given by = P( $\bar X$ > 84 min)

P( $\bar X$ > 84 min) = P( $\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }$ > $\frac{84-75}{\frac{20}{\sqrt{20} } }$ ) = P(Z > 2.01) = 1 - P(Z $\leq$ 2.01)

= 1 - 0.9778 = 0.0222

The above probability is calculated by looking at the value of x = 2.01 in the z table which has an area of 0.9778.

(d) When increasing the sample size, the probability decreases because the variability in the sample mean decreases as we increase the sample size which we can clearly see in part (b) and (c) of the question.

(e) Since it is clear that the probability that a random sample of 20 time intervals between irruption has a mean longer than 84 minutes is very slow(less than 5%0 which means that this is an unusual event. So, we can conclude that the population mean may be larger than 75 minutes between irruption.

8 0

3 years ago

What is the prime factorization of 45/72

emmainna [20.7K]

5/8 I believe. You can divide both by 9

4 0

3 years ago

An ice cream shop has 5 flavors. Carlos wants to buy a five-scoop cone with 5 different flavors. How many cones could he buy if

icang [17]

I think the answer is E

3 0

3 years ago

X+2y=19 and x+y=13 in substitution methood​

X+2y=19 and x+y=13 in substitution methood