The earth is 146 million kilometers from the sun, and neptune is 4.5 billion kilometers from the sun. what is the difference in these two distances expressed in scientific notation?

a) 4.354 x 10⁹ km
b) 4.354 x 10⁸ km
c) 4.354 x 10⁷ km
d) 4.364 x 10⁹ km

!

4.5 billion minus 146 million equals 4354000000. Then you must express it in scientific notation. To do this you move the decimal point so that there is only one number in front of it. Then count how many spaces you moved it and that will be your exponent. If you moved the exponent to the left then the exponent is positive, if you moved the point to the right then the exponent is negative. The format in scientific notation is: all of the numbers are included until the rest are zeros x 10^(to the power of) the number of places you moved the decimal. 

So, in this problem, your answer is A.