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3 years ago

Need help any body help please

Mathematics

1 answer:

lutik1710 [3]3 years ago

6 0

For the first one (aka 7) you would write 10² wich is the same as 10×10 and so the answer is 100

For the second one (aka 8) you would write 3×3×3×3×3×3×3×3×3 and the answer is 486 square miles

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How many pounds of a 15% copper alloy must be mixed with 700lb of a 30% copper alloy to maybe a 25.5% copper alloy

lisov135 [29]

Answer:

$300\; \rm lb$ .

Step-by-step explanation:

Let $x$ represent the mass (in pounds) of that $15\%$ copper alloy required, such that the final mixture would contain $25.5\%$ copper by mass.

Consider: if $x$ pounds of that $15\%$ copper alloy is mixed with $700$ pounds that $30\%$ copper alloy, what would be the mass of copper in the mixture?

Mass of copper in $x$ pounds of that $15\%$ copper alloy: $(0.15\, x)\; \rm lb$ .
Mass of copper in $700$ pounds of that $30\%$ copper alloy: $700 \times 0.30 = 210\; \rm lb$ .

Therefore, the mixture would contain $(210 + 0.15\, x) \; \rm lb$ of copper.

The mass of that mixture would be $(700 + x)\; \rm lb$ . The mass fraction of copper in that mixture would be:

$\displaystyle \frac{(210 + 0.15\, x)\; \rm lb}{(700 + x)\; \rm lb} \times 100\%$ .

This ratio is supposed to be equal to $25.5\%$ . These two pieces of equations combine to give an equation about $x$ :

$\displaystyle \frac{(210 + 0.15\, x)\; \rm lb}{(700 + x)\; \rm lb} \times 100\% = 25.5\%$ .

$\displaystyle \frac{210 + 0.15\, x}{700 + x} = 0.255$ .

Simplify and solve for $x$ :

$210 + 0.15\, x= 0.255\, (700 + x)$ .

$(0.255 - 0.15)\, x= 210 - 0.255 \times 700$ .

$\displaystyle x = \frac{210 - 0.255 \times 700}{0.255 - 0.15} = 300$ .

Therefore, $300\; \rm lb$ of that $15\%$ alloy would be required.

4 0

2 years ago

4/ PLEASE HELP ME ON THIS. ASAP

rewona [7]

Answer: a,b,d,e are all right beacuse they all relate to the question

Step-by-step explanation:

c how ever is no shown on the graph and is therefor wrong

4 0

2 years ago

Which pairs of rational numbers are equivalent? Select all that apply.

ser-zykov [4K]

-0.5 is equivalent to - 1/2

8 0

3 years ago

Read 2 more answers

Find the probability that the mean annual preciptiation will be between 32 and 34 inches. variable is normally distributed

liq [111]

Supposing, for the sake of illustration, that the mean is 31.2 and the std. dev. is 1.9.

This probability can be calculated by finding z-scores and their corresponding areas under the std. normal curve.
34 in - 31.2 in
The area under this curve to the left of z = -------------------- = 1.47 (for 34 in)
1.9
32 in - 31.2 in
and that to the left of 32 in is z = ---------------------- = 0.421
1.9

Know how to use a table of z-scores to find these two areas? If not, let me know and I'll go over that with you.

My TI-83 calculator provided the following result:

normalcdf(32, 34, 31.2, 1.9) = 0.267 (answer to this sample problem)

5 0

2 years ago

Mrs. Jones wants to cover half of her 5 x 7 rectangular bulletin board with two different colors (white and black) as show in th

Vladimir [108]

5x7=35
35/2= 17.5(whichever unit you’re using)

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2 years ago