If a computer can do a calculation in 0.000003 second, how long, in seconds, would it take the computer to do 9 billion (9 comma 000 comma 000 comma 000) calculations? write your answer in scientific notation.

First write the 9 billion in scientific notation. There are 9 zeros so 9 * 10^9 is how you would write 9 billion.  

Now write 0.000003 in scientific notation. Little trickier. There are 5 zeros. But that will only take you to 0.3 You have to add 1 more to get to a number between 1 and 10. So 0.000003 = 3*10^-6 is how that number would be written in scientific notation.

Comp_Time = time for 1  computation / sec * the number of computations.

Comp_Time = 3*10^-6 * 9*10^9 = 27 * 10^3 = 2.7 * 10^4 seconds. That's an awfully long time for 9 billion calculations but that's what the numbers give us.

Answer 2.7 * 10^4 seconds = 7.5 hours.