9 yards are the same as 27 (9·3) feet, and 48 feet are equal to 16 (48:3) yards.
To express a ratio we've to convert these figures into the simplest available ones, so, let's simplify using the smallest numbers, 9 yards to 16 yards.
9 is divisible by 3 only, and 16 can be divided by 2, 4, and 8. That means we cannot use a common denominator, so the simplest ratio will be the one we already have: 9/16.
