Diane bought 9 barrettes that each cost the same amount. The total cost was $3.51. What was the price of each barrette?

To find the price of each barrette, we divide the total cost by the number of barrettes: $3.51/9 barrettes = $<<3.51/9=0.39>>0.39 per barrette. Answer: \boxed{0.39}.