4. Graphite is made up of layers of graphene. Each layer of graphene is about 200 picameters, or $200 \times 10^{- 12}$ meters, thick. How many layers of graphene are there in a 1.6-mm-thick piece of graphite? Express your answer in scientific notation.
(From Unit 7, Lesson 14.)

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Answer

$8.00 \times 10^{3}$ layers of graphene in a 1.6-mm-thick piece of graphite.

Steps

Step 1 ：Convert the thickness of the graphite piece to picometers: $1.6 mm = 1.6 \times 10^{6} pm$

Step 2 ：Divide the thickness of the graphite piece by the thickness of one graphene layer: $\frac{1.6 \times 10^{6} pm}{200 pm} = 8 \times 10^{3}$

Step 3 ： $8.00 \times 10^{3}$ layers of graphene in a 1.6-mm-thick piece of graphite.