Samuel swept the porch and cleared nine-tenths of the dust particles from it. As he walked across the porch afterward, his shoes left 223 dust particles behind. How many dust particles were on the porch before Samuel swept if there were 331 after he walked across it? Think carefully first, then make a decision:
Before Samuel walked across the porch, there were 331 - 223 = 108 dust particles. Those 108 were 1 / 10 of the original amount, so there were 108 * 10 = 1080 dust particles on the porch before Samuel swept. So, the answer is 1080.