A virus has diameter $2 \times 10^{-7}$ m. End-to-end, how many viruses span 1 mm?

A virus has diameter $2 \times 10^{-7}$ m. End-to-end, how many viruses span 1 mm?
  1. $5{,}000$
  2. $500$
  3. $50{,}000$
  4. $50$

Solution

$1$ mm $= 10^{-3}$ m. Number $= \dfrac{10^{-3}}{2 \times 10^{-7}} = 0.5 \times 10^{4} = 5000$.

Asked in: NSO

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