Converting to SI units w/ significant digits & scientific notation

[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?

My answer:
3.15 * 10^{7}
Book's answer:
3.16 * 10^{7}

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

 

[Chestermiller]

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

Chet

 

[delgeezee]

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

Chet

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.

 

[gneill]

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.

You might say it's a bit of a leap