# Converting to SI units w/ significant digits & scientific notation

1. May 11, 2012

### delgeezee

Hi.
I'm asked to convert 2 year into the SI Unit seconds:

Known:
1 Hr = 3600 s
1 Day = 86400 s

So using a calculator....
1 yr = 365*86,400 = 31,536,000

I want to express the answer in scientific notation:

Because the lesser number on has 3 significant digits, the scientific notation will also be expressed w/ 3 significant digits. Correct?

The coefficient in scientific notation must be greater then 1 and less then 10. Correct?

$3.15 * 10^{7}$
$3.16 * 10^{7}$

Why does the book's answer have it rounded up?

2. May 11, 2012

### Staff: Mentor

They must have used 365.25 days for the length of a year.

Chet

3. May 11, 2012

### delgeezee

Thank you for the reply. At first I thought you were joking & the book made no mention. I had no idea 365.25 is the average number of days in a year.

4. May 11, 2012

### Staff: Mentor

You might say it's a bit of a leap