compare the method of using expanded form and the method of using place value to multiply a decimal and a whole number

1 answer:

3 0

Unfortunately, multiplying and dividing decimals this effect does not occur. In some cases, the decimal number even complicates the operatsii.Dlya beginning, we introduce a new definition. We will meet him very often, and not only in this part of uroke.Znachaschaya - is all that is between the first and the last non-zero digit, including the ends. It's only about numbers, the decimal point is not uchityvaetsya.Tsifry included in the meaningful part of the number, are called significant figures. They may be repeated or even be zero.

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An athlete's speed on her bike is 14mph faster than her average speed running. She can bike 31.5 miles in the same time that it

scoundrel [369]

You would cross multiply.
14 over 31.5
and X over 10.5
10.5 times 14 is 147
divide that by 31.5 which is 4 1/3
and that is how fast she can run
4 1/3 mph

7 0

3 years ago

You are a lifeguard and spot a drowning child 60 meters along the shore and 40 meters from the shore to the child. You run along

sukhopar [10]

Answer:

The lifeguard should run across the shore a distance of 48.074 m before jumpng into the water in order to minimize the time to reach the child.

Step-by-step explanation:

This is a problem of optimization.

We have to minimize the time it takes for the lifeguard to reach the child.

The time can be calculated by dividing the distance by the speed for each section.

The distance in the shore and in the water depends on when the lifeguard gets in the water. We use the variable x to model this, as seen in the picture attached.

Then, the distance in the shore is d_b=x and the distance swimming can be calculated using the Pithagorean theorem:

$d_s^2=(60-x)^2+40^2=60^2-120x+x^2+40^2=x^2-120x+5200\\\\d_s=\sqrt{x^2-120x+5200}$

Then, the time (speed divided by distance) is:

$t=d_b/v_b+d_s/v_s\\\\t=x/4+\sqrt{x^2-120x+5200}/1.1$

To optimize this function we have to derive and equal to zero:

$\dfrac{dt}{dx}=\dfrac{1}{4}+\dfrac{1}{1.1}(\dfrac{1}{2})\dfrac{2x-120}{\sqrt{x^2-120x+5200}} \\\\\\\dfrac{dt}{dx}=\dfrac{1}{4} +\dfrac{1}{1.1} \dfrac{x-60}{\sqrt{x^2-120x+5200}} =0\\\\\\ \dfrac{x-60}{\sqrt{x^2-120x+5200}} =\dfrac{1.1}{4}=\dfrac{2}{7}\\\\\\ x-60=\dfrac{2}{7}\sqrt{x^2-120x+5200}\\\\\\(x-60)^2=\dfrac{2^2}{7^2}(x^2-120x+5200)\\\\\\(x-60)^2=\dfrac{4}{49}[(x-60)^2+40^2]\\\\\\(1-4/49)(x-60)^2=4*40^2/49=6400/49\\\\(45/49)(x-60)^2=6400/49\\\\45(x-60)^2=6400\\\\$

$x$

As $d_b=x$ , the lifeguard should run across the shore a distance of 48.074 m before jumpng into the water in order to minimize the time to reach the child.

7 0

3 years ago

Is the difference of two positive rational number always positive explain

Dominik [7]

No . . . while the difference represents the absolute magnitude between two numbers . . . for example . . .

The difference between 5 and 2 is . . . 3
The difference between 6.4 and 9.5 is . . . 3.1

. . . there is still the chance that the difference may be zero . . . in which case the difference is neither positive nor negative

. . . so in short . . . the answer is . . . NO

5 0

3 years ago

What is the answer??? P-6+2=-4+10

miskamm [114]

Answer:p=6-2-4+10

P=4-4+10

P=10

Step-by-step explanation:

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3 years ago

Cost of an airplane flight increase from $250 to $260. What is the percentage increase?

Sedaia [141]