There are 420 balls in a ball pool. There is a combination of violet, blue, yellow and green balls. 2/7 are violet, 35% are blue and the ratio of yellow to green is 4:5. How many of each colour ball is there in the ball pool?

Together, the total number of balls is 420. 2/7 of the total 420 balls are violet. Therefore the number of violet balls can be calculated by the equation 2/7 x 420/1 = 840/7=120. There are 120 violet balls in the pool. 35% of the total 420 balls are blue. We can calculate what 35% is easily by calculating what 10% and 5% of 420 is. 10% of 420 is 42 (420/10 = 42) and 5% of 420 is 21 (10%/2 which is 42/2 = 21 ). (10%3)+5%=35% , (423)+21 = 147. There are 147 blue balls in the pool.  420-(120+147) = 153With 120 violet and 147 blue balls, the remaining 153 balls are a combination of yellow and green balls . The ratio of Yellow: Green is 4:5, making a group of 9 balls in total. 4+5 = 9153/9 = 17. Meaning out of the remaining balls, there are 17 groups of yellow/green, where there are 4 yellow and 5 green in each group.4 17 = 68 . There are 68 yellow balls. 517 = 85  There are 85 green balls