# How do you write 72times10^4 in scientific notation?

$7.2 \times {10}^{5}$

#### Explanation:

When writing a number in scientific notation, we have two parts:

• the "number" part that shows all the digits we need to see (so in this case they are "7" and "2") and is expressed as a number between 0 and 10. In our case we'll express the number as 7.2, and
• the number of times we needed to move the decimal to get the "number" to be between 0 and 10. Since we are moving the decimal one place to the left, we need to increase the power by 1. It's already showing a power of 4, so we'll change that to 5.

So, $72 \times {10}^{4} = 7.2 \times {10}^{5}$

As a side note, to help see this works:

$7.2 \times {10}^{5} = 72 \times {10}^{4} = 720 \times {10}^{3} = 7200 \times {10}^{2} = 72 , 000 \times {10}^{1} = 720 , 000$

The 72 never changes - it's only where the decimal place sits (and putting in the needed number of 0's so that it can be seen).