To determine how many scrapbooks the student can decorate, we need to divide the total length of ribbon on the spool (1/2 yard) by the amount of ribbon used for each scrapbook (1/4 yard).
Dividing 1/2 yard by 1/4 yard gives us:
(1/2) ÷ (1/4) = (1/2) × (4/1) = 2 × 4 = 8
Therefore, the student can decorate 8 scrapbooks using all the ribbon on the spool.