A doctor suspects that one of her patients has a strep infection. A lab report shows that the patient’s white blood cell count is 12,000 cells per microliter. The normal range for the white blood cell count is between 4.5 billion and 10 billion cells per liter. Do the results indicate an infection? First, convert the lab result from cells per microliter to cells per liter. The lab result shows 12,000 cells in one microliter of the patient’s blood. How many cells are in one liter of the patient’s blood? (A liter contains 1,000,000 microliters.)

12,000

12,000,000

12,000,000,000

12,000,000,000,000