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The ratio of blue to black jeans at a certain shop is 15:16. If there were 35 additional black jeans in the shop, the ratio of blue to black jeans would be 15:21. How many blue jeans does the shop have?

Let Blue/Black original value, \(\frac{15}{16}\)= \(\frac{15x}{16x}\)
By data,
16x=16x+35
\(\frac{15x}{16x+35}\)=\(\frac{15}{21}\)
Solving above, x=7
Blue= 15x=15*7=105
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Given :
Initial ratio of Jeans (Blue:Black = 15x:16x)
Final ratio of Jeans (Blue:Black = 15x:21x)

Hence difference of 21x - 16x is caused by the addition of the 35 black jeans, x = 7.
Hence the blue jeans is 15x = 105(Option C)
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The ratio of blue to black jeans at a certain shop is 15:16. If there were 35 additional black jeans in the shop, the ratio of blue to black jeans would be 15:21. How many blue jeans does the shop have?

A) 100
B) 103
C) 105
D) 107
E) 110

15 + 16 = 31
15 + 21 = 36

SO, 5 represents 35 Black jeans or 1 represents 7 Black jeans , as no blue jeans were added...

So, the total number of blue jeans is 15*7 = 105 Blue Jeans...

Answer will be (C)
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Blue/Black (x/y)=15\16
If additional 35 black jeans are added the ration becomes
(x/y+35)=15/21

Solving for X and Y We get number of blue jeans 105
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danlew
The ratio of blue to black jeans at a certain shop is 15:16. If there were 35 additional black jeans in the shop, the ratio of blue to black jeans would be 15:21. How many blue jeans does the shop have?

A) 100
B) 103
C) 105
D) 107
E) 110

We are given that the ratio of blue to black jeans at a certain shop is 15x : 16x. We are also given that if there were 35 additional black jeans in the shop, the ratio of blue to black jeans would be 15 : 21. Thus:

15x/(16x + 35) = 15/21

15x/(16x + 35) = 15/21

15x(21) = 15(16x + 35)

21x = 16x + 35

5x = 35

x = 7

Thus, the shop has 15(7) = 105 blue jeans.

Answer: C

(Note: We also could have recognized that the number of blue jeans must be a multiple of 15 and the only answer choice that is a multiple of 15 is answer choice C, 105.)
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danlew
The ratio of blue to black jeans at a certain shop is 15:16. If there were 35 additional black jeans in the shop, the ratio of blue to black jeans would be 15:21. How many blue jeans does the shop have?

A) 100
B) 103
C) 105
D) 107
E) 110

Here's a solution that uses two variables:

The ratio of blue to black jeans at a certain shop is 15:16
Let B = number of blue jeans PRESENTLY in the shop
Let K = number of black jeans PRESENTLY in the shop
So, we can write: B/K = 15/16
Cross multiply to get: 16B = 15K

If there were 35 additional black jeans in the shop, the ratio of blue to black jeans would be 15:21.
So, B = number of blue jeans in the shop AFTER 35 black jeans are added
And K + 35 = number of black jeans in the shop AFTER 35 black jeans are added
So, we can write: B/(K + 35) = 15/21
Cross multiply to get: 21B = 15(K + 35)
Expand: 21B = 15K + 525
Subtract 525 from both sides to get: 21B - 525 = 15K

How many blue jeans does the shop have?
We now have the following system of equations:
16B = 15K
21B - 525 = 15K

Since both equations are set equal to 15K, we can write: 16B = 21B - 525
Subtract 21B from both sides: -5B = -525
Divide both sides by -5 to get: B = 105

Answer:
Cheers,
Brent
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RaguramanS
The ratio of blue to black jeans at a certain shop is 15:16. If there were 35 additional black jeans in the shop, the ratio of blue to black jeans would be 15:21. How many blue jeans does the shop have?

Let Blue/Black original value, \(\frac{15}{16}\)= \(\frac{15x}{16x}\)
By data,
16x=16x+35
\(\frac{15x}{16x+35}\)=\(\frac{15}{21}\)
Solving above, x=7
Blue= 15x=15*7=105

Why did we add X to the numerator and denominator in the fraction?
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danlew
The ratio of blue to black jeans at a certain shop is 15:16. If there were 35 additional black jeans in the shop, the ratio of blue to black jeans would be 15:21. How many blue jeans does the shop have?

A) 100
B) 103
C) 105
D) 107
E) 110


it took time to solve this question but i was able to make out that answer choice will be multiple of 5, having see the numbers... 35 and 15. and choose C correctly.
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danlew
The ratio of blue to black jeans at a certain shop is 15:16. If there were 35 additional black jeans in the shop, the ratio of blue to black jeans would be 15:21. How many blue jeans does the shop have?

A) 100
B) 103
C) 105
D) 107
E) 110

Answer will remain a multiple of 15. Because there is no change on that one.
Hence C
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