If one container holds 55 balls, how many balls will nine containers hold? a. 395 b. 455 c. 355 d. 495

D, 495.

9 x 55 = 495, so nine containers can hold 495 balls.

You can either use a ratio, or just multiply. But, a ratio does lead to multiplying in this situation.
1 Container : 55 balls; This is the ratio for one container.
9 Containers : Y balls; This is the ratio we're trying to solve, y is the number we're trying to solve.
Since you're multiplying the container by 9, you need to multiply the balls by 9.
55×9
495.
So D. 495 balls are in 9 containers.