Every disk in a bag is either blue, yellow or green. The ratio of blue disks to yellow disks to green disks in this bag is 3 : 7 : 8. If the total number of disks in the bag is 90, how many more green disks than blue disks are in the bag?

A. 25
B. 28
C. 30
D. 35
E. 40
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Blue ......... Yellow ........ Green ......... Total

3x ............... 7x ............. 8x ............... 90

Require to find 8x - 3x = 5x

18x = 90

\(5x = \frac{90}{18} * 5\)

= 25

Answer = A
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The ratio of blue disks to yellow disks to green disks in this bag is 3 : 7 : 8, which means that for every 3 blue disks, we have 7 yellow disks, and 8 green disks. Since this is a ratio, we can let the number of blue disks in the bag be 3x, the number of yellow disks be 7x, and the number of green disks be 8x. So 3x + 7x + 8x = 90. If we simplify the equation we get 18x = 90. We can then divide both sides by 18. So . In order to solve for the number of disks, replace x with 5. Therefore the number of green disks is 8x = 8(5) = 40 and the number of blue disks is 3x = 3(5) = 15. The number of green disks is greater than the number of blue disks by 40 - 15 = 25.
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