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kondaur [170]
2 years ago
14

Jake made a total of 7 copies at a copy shop, with some being black-and-white copies and some being color copies. Black-and-whit

e copies cost 8 cents, and color copies cost 15 cents. If Jake spent a total of 70 cents on copies, which system of equations can be used to determine the number of black-and-white copies and the number of color copies he made? Assume b is the number of black-and-white copies and c is the number of color copies.
Mathematics
2 answers:
Arada [10]2 years ago
8 0
Jake spent a total of 70 cents.
b = black-and-white = 8 cents
c = color = 15 cents

70 = 8b + 15c

he made a total of 7 copies
b + c = 7

system of equation:
70 = 8b + 15c
b + c = 7

--------------------------

b + c = 7
b + c (-c) = 7 (-c)
b = 7 - c

plug in 7 - c for b

70 = 8(7 - c) + 15c
Distribute the 8 to both 7 and - c (distributive property)

70 = 56 - 8c + 15c
Simplify like terms

70 = 56 - 8c + 15c
70 = 56 + 7c

Isolate the c, do the opposite of PEMDAS: Subtract 56 from both sides

70 (-56) = 56 (-56) + 7c
14 = 7c

divide 7 from both sides to isolate the c

14 = 7c
14/7 = 7c/7
 c = 14/7
 c = 2

c = 2
---------------

Now that you know what c equals (c = 2), plug in 2 for c in one of the equations.
b + c = 7
c = 2
<em>b + (2) = 7
</em><em />Find b by isolating it. subtract 2 from both sides
b + 2 = 7
b + 2 (-2) = 7 (-2)
b = 7 - 2
b = 5

Jake made 5 black-and-white copies, and 2 color copies

hope this helps
Vesnalui [34]2 years ago
8 0

Answer:

a

Step-by-step explanation:

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Answer:

volume of trapezoidal prism = 15x^2 cubic units

Step-by-step explanation:

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Parallel sides measure x and 2x, for an average of 1.5x.

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Sienna planned a rectangular pool, as shown in the scale drawing below.
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Answer:

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Explanation:

Whenever you are calculating factors, you are comparing two measurements. In this problem we compared a longer length to a shorter length pool. The length was changed to (27.5 feet) and youre comparing to the length it was originally (22 feet).

Ok so you know the two measurements being compared, but how come it’s 27.5/22 and not 22/27.5? Because the value got bigger.

In this problem you had a pool with long side of 22 ft. But then you made it longer to 27.5 ft. So it scales up,

It went from 100% its length to 125% its length. So the length is 125% / 100% = 1.25 times longer than it used to be.

Here’s another example:

How do you calculate your grade percentage on a test? You take the amount of points you earned and divide by the total possible points. Your grade percentage is a comparison of your score (Compare value) compared to a perfect score (reference value) .

So lets say your test had 22 total points. You get all the answers correct so you get 22/22 points which is 22/22*100 = 100%. Let’s say you get an extra bonus question correct so you end up with even more points and you get 27.5 points out of 22. By getting the bonus points you scaled up your score! Now your score is 27.5/22 * 100 = 125%. So you went from 100% to a 125%. Or from a scale factor of 1 to 1.25.

Whenever the value is getting bigger than it was, you’re going to have a compared percentage over 100%. If the value gets smaller, then you would get a compared percentage less than 100%. Similarly a factor scale is going to be over 1 if the compared value is getting bigger, and less than 1 if it’s getting smaller.

So you don’t need to use percentages, factors are the same they just look a little different.

27.5/22 = 125% / 100% = 1.25

In summary just do this division:

(compare value)/(reference value). The result is how big the top value is compared to the bottom value.

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