If we multiply 3⅓ minutes by 3 we get 10 minutes. So the machine will make 3 times as many pencils, which is 3×2½ or 3×2 plus 3 times ½, which is 6+1½=7½ pencils. So in 10 minutes the machine makes 7½ pencils. In 2 minutes it makes 5 times fewer pencils so we divide 7½ by 5. We can break (not literally!) 7½ pencils into 15 half pencils, and 15/5=3. So in 2 minutes the machine makes 3 half pencils or 3/2 pencils which is 1½ pencils.