Question

The width of a red blood cell is approximately 8 micrometers, which is 8 x 10-6 meter. Give your answers to the questions below in scientific notation. Be sure to answer both A and B, and explain your answer to B.

A. What would be the width of 7.2 x 105 red blood cells in meters?


B. If a grain of salt is .5mm wide, how many red blood cells could fit across one grain of salt? Explain your answer. (Hint: 1mm = 1 X 10-3 m.)

Answer 1

A. 756

B. 69.44 or 62.5

Explanation:

To get the answer for B you first convert 0.5mm to micrometers.

0.5 millimeters = 500 micrometers

Now, we divide 500 by 8

500 ÷ 8 = 62.5

To get the exact result, we divide 500 by 7.2

500 ÷ 7.2 = 69.44

Answer 2

A)
`5.76\text{ meters}`

B) 62

Explanation:

The width of a red blood cell is approximately 8 micrometers
`=8* 10^(-6)` meters

Part A)

Width of 1 red blood cell
`=8* 10^(-6)` meters

width of
`7.2* 10^5` red blood cells
`=7.2* 10^5* 8* 10^(-6)` meters

`=7.2* 8* 10^5* 10^(-6)`

`=57.6* 10^(-1)`

Now change into scientific notation. So, decimal should be between 1 to 10

Decimal move 1 digit right to left

`=5.76* 10^1* 10^(-1)`

`=5.76\text{ meters}`

Hence, the width of red blood cells is
`5.76\text{ meters}`

Part B)

If a grain of salt is 0.5 mm wide.

First convert mm to m. ( 1 mm = 1 × 10⁻³ m)

Therefore, 0.5 mm = 5 × 10⁻⁴ m

`\text{Number of red blood cells fit}=\frac{\text{Size of grain}}{\text{Size of a red blood cell}}`

Size of a grain = 5 × 10⁻⁴ m

Size of a blood cell = 8 × 10⁻⁶ m

`\text{Number of red blood cells fit}=(5* 10^(-4))/(8* 10^(-6))`

`\text{Number of red blood cells fit}=62.5`

Hence, 62 number of red blood cells fit in a grain of salt.