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3 years ago

PLZ HELP ASAP!!!! What is 20x(8+4) x 9

Mathematics

1 answer:

dolphi86 [110]3 years ago

8 0

Answer:

1440x+720

Step-by-step explanation:

Expanding up the brackets, you get

160x+80.

Then you multiply the whole thing by 9.

9(160x+80)=

1440x+720

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A baseball diamond is a square with side 90 ft. A batter hits the ball and runs toward first base with a speed of 31 ft/s. (a) A

julsineya [31]

Answer:

a) -13.9 ft/s

b) 13.9 ft/s

Step-by-step explanation:

a) The rate of his distance from the second base when he is halfway to first base can be found by differentiating the following Pythagorean theorem equation respect t:

$D^{2} = (90 - x)^{2} + 90^{2}$ (1)

$\frac{d(D^{2})}{dt} = \frac{d(90 - x)^{2} + 90^{2})}{dt}$

$2D\frac{d(D)}{dt} = \frac{d((90 - x)^{2})}{dt}$

$D\frac{d(D)}{dt} = -(90 - x) \frac{dx}{dt}$ (2)

Since:

$D = \sqrt{(90 -x)^{2} + 90^{2}}$

When x = 45 (the batter is halfway to first base), D is:

$D = \sqrt{(90 - 45)^{2} + 90^{2}} = 100. 62$

Now, by introducing D = 100.62, x = 45 and dx/dt = 31 into equation (2) we have:

$100.62 \frac{d(D)}{dt} = -(90 - 45)*31$

$\frac{d(D)}{dt} = -\frac{(90 - 45)*31}{100.62} = -13.9 ft/s$

Hence, the rate of his distance from second base decreasing when he is halfway to first base is -13.9 ft/s.

b) The rate of his distance from third base increasing at the same moment is given by differentiating the folowing Pythagorean theorem equation respect t:

$D^{2} = 90^{2} + x^{2}$

$\frac{d(D^{2})}{dt} = \frac{d(90^{2} + x^{2})}{dt}$

$D\frac{dD}{dt} = x\frac{dx}{dt}$ (3)

We have that D is:

$D = \sqrt{x^{2} + 90^{2}} = \sqrt{(45)^{2} + 90^{2}} = 100.63$

By entering x = 45, dx/dt = 31 and D = 100.63 into equation (3) we have:

$\frac{dD}{dt} = \frac{45*31}{100.63} = 13.9 ft/s$

Therefore, the rate of the batter when he is from third base increasing at the same moment is 13.9 ft/s.

I hope it helps you!

4 0

3 years ago

Read 2 more answers

Queston 132

Sever21 [200]

Answer:

68cm^2

Step-by-step explanation:

<h2>A trapezium is a type of quadrilateral with the two opposite sides parallel.</h2>

Area of a trapezium= 1/2(sum of parallel sides)×height

Area of the trapezium= 1/2(5+3)×17

Area of the trapezium= 1/2(8)×17

Area of the trapezium=4×17= 68cm^2

4 0

2 years ago

Which of the following estimates at a 95% confidence level most likely comes from a small sample

Nikitich [7]

Answer:

Answer is c

Step-by-step explanation:

In hypothesis testing whether to accept or reject null hypothesis, normally we find one method as using confidence interval. If the test statistic lies within confidence interval, we accept otherwise we reject.

For arriving confidence intervals we add and subtract margin of error from the mean we use in null hypothesis.

Margin of error = std error * critical value of test (Z or t etc)

For the same std deviation, std error = std dev/sq rt of sample size

Thus std error is inversely proportional to the square root of sample size.

If n becomes larger, std error becomes smaller and vice versa.

So margin of error increases for smaller sample size.

Since we have to select confidence level from a small sample, we have to select one which has the greatest margin of error=18

Hence answer is

c) 71%(+/-18%)

5 0

3 years ago

The vertex of a parabola will never be on the axis of symmetry.<br> true or false

Gala2k [10]

False, it's always on the vertex of the parabola.

4 0

4 years ago

Which equation represents a linear function with a slope of 12 and a y-intercept of -15?

LUCKY_DIMON [66]

Answer:

Answer is A, top left box.

Step-by-step explanation:

the slope is 1/2 and the slope is always to the right of m

5 0

3 years ago

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