Final answer:
Sydney spent 0.625 hours practicing piano.
Step-by-step explanation:
To find out how many hours Sydney spent practicing piano, we first need to calculate 1/4 of the total time Sydney spent practicing music.
Sydney spent 2 1/2 hours practicing music, which is the same as 2 hours and 30 minutes.
To find 1/4 of the time, we divide the total time by 4: 2.5 hours / 4 = 0.625 hours.
Therefore, Sydney spent 0.625 hours practicing piano.