Laboratory Mathematics and Calculations Flashcards

An incubator is set at 37°C. What is this temperature in degrees Fahrenheit?

Answer: 98.6°F

°F = (°C × 9/5) + 32 = 66.6 + 32 = 98.6°F.

A 100 mg/dL standard has an absorbance of 0.50, and an unknown has an absorbance of 0.30. What is the unknown concentration?

Answer: 60 mg/dL

By Beer's law, Cu = (Au/As) × Cs = (0.30/0.50) × 100 = 60 mg/dL.

In a manual WBC count with a 1:20 dilution, 200 cells are counted in 4 large squares (each 1 mm², 0.1 mm deep). What is the WBC count?

Answer: 10,000/µL

Cells/µL = (200 × 20) / (4 mm² × 0.1 mm) = 4000 / 0.4 = 10,000/µL.

A centrifuge with a 10 cm rotor radius spins at 3,000 rpm. Approximately what is the relative centrifugal force (RCF = 1.118 × 10^-5 × r × rpm²)?

Answer: 1,006 × g

1.118 × 10^-5 × 10 × 9,000,000 ≈ 1,006 × g.

A solution transmits 10% of incident light. What is its absorbance?

Answer: 1.0

A = 2 − log(%T) = 2 − log(10) = 2 − 1 = 1.0.

How much 95% ethanol is needed to prepare 100 mL of 70% ethanol?

Answer: 73.7 mL

V1 = (70 × 100) / 95 = 73.7 mL, then dilute to 100 mL with water.

A patient's reticulocyte count is 3% with a hematocrit of 30%. Using a normal hematocrit of 45%, what is the corrected reticulocyte count?

Answer: 2.0%

Corrected retic = 3% × (30/45) = 2.0%.