Answer:
1000 balls
(there are infinitely many solutions to this question; you can scale up 1000, use a different total, etc.)
Step-by-step explanation:
there are, of course, multiple possible numbers,
but the easiest way is to go with 1000, because we can say 375 / 1000 and 400 / 1000
(0.4 + 0.275 + 0.225 = 1)
400 out of 1000 balls are red (400/1000 = 4/10 = 0.4)
375 out of 1000 balls are green (375/1000 = 3.75/10 = 0.375)
225 out of 1000 balls are yellow (225/1000 = 2.25/10 = 0.225)
the question never gave detail as to if the answer should be the <em>lowest</em><em> </em>number of possible balls, so this value is possible.
So, a possible number of balls in this bag is 1000.