In a box, there are chocolate bars of 3 colours, green, blue and black. There are 680 less black chocolate bars than blue chocolate bars. The number of black chocolate bars is ¹₂ more than the green chocolate bars. Given that the number of black chocolate bars is 12% of the total number of chocolate bars in the box, how many less green chocolate bars are there than blue chocolate bars?

Green chocolate bars	Blue chocolate bars	Black chocolate bars
	1 u + 680	1 u
2x4		3x4
88%		12%
8%	80%	12%

1 + ¹₂ = ²₂ + ¹₂ = ³₂

Yellow chocolate bars : Purple chocolate bars = 2 : 3

The number of black chocolate bars is repeated.  Make the number of black chocolate bars the same.

3 x 4 = 12%

Total number of green chocolate bars and blue chocolate bars in percent
= 100% - 12%
= 88%

Number of blue chocolate bars in percent
= 88% - 8%
= 80%

Number of more blue chocolate bars than black chocolate bars in percent
= 80% - 8%
= 68%

68% = 680

1% = 680 ÷ 68 = 10

Number of less green chocolate bars than blue chocolate bars
= 80% - 8%
= 72%
= 72 x 10
= 720

Answer(s): 720