scientific notation
posted by cathey .
the speed of light is1.86 times 10^5 miles per second. using a year of 365 days, how far does light travel in a year?

Multiply that speed by the number of seconds in a year, which is 365x24x3600 = ____
Express the result in scientific notation, _.__x10^_
The answer will be the length of a light=year, in miles.
Compare your answer with
http://www.universetoday.com/39630/lightyearinmiles/ 
Unless you have been told otherwise I would recommend that you include the units in a conversion such as this. While it might seem pedantic here, it can help a great deal when the units are less familiar.
365 d y^1 x 24 h d^1 x 60 min h^1 x 60 s min^1 = ___ s y^1 
7.34 x 10^26 atoms of Cu is equivalent to how many moles of Cu? (Express to 3 sf)