Question

Write the lengths of the three eras in scientific notation. Order the lengths from least to greatest.

Answer 1

`\begin{gathered} Cenozoic\colon$\quad 6.55*10^7$\; years\; ago \\ Mesozoic\colon$\quad 2.51*10^8$\; years\; ago \\ Paleozoic\colon$\quad 5.42*10^8$\; years\; ago \end{gathered}`

Explanation:

A number is said to be in scientific notation when it is written as a product of a number between 1 and 10 and a power of 10.

Given the lengths of the three eras below:

`\begin{gathered} Paleozoic\colon$\quad 5.42*10^8$\; years\; ago \\ Cenozoic\colon$\quad 6.55*10^7$\; years\; ago \\ Mesozoic\colon$\quad 2.51*10^8$\; years\; ago \end{gathered}`

Each of the numbers is already written in scientific notation.

Next, we order the lengths from least to greatest.

• For two numbers in scientific notation, the number with a lower power of 10 is smaller, so the Cenozoic era comes first.

,

• For two numbers in scientific notation with the same power of 10, 2.51 is lower than 5.42, so the length of the Mesozoic era is less than the length of the Paleozoic era.

Thus, the lengths are ordered as shown below:

`\begin{gathered} Cenozoic\colon$\quad 6.55*10^7$\; years\; ago \\ Mesozoic\colon$\quad 2.51*10^8$\; years\; ago \\ Paleozoic\colon$\quad 5.42*10^8$\; years\; ago \end{gathered}`