The Grand Canyon is about 1.6×103 meters deep. Scientists think that the Colorado River has been eroding the Grand Canyon for 4.0×106 years. According to these scientists, what is the approximate average rate of erosion written in scientific notation?

So start with your standard numbers. Divide 1.6 by 4 and you get 0.4

With the exponents, since you’re dividing, you keep the base and subtract the exponents. So 3-6=-3

You’d get 0.4 x 10 to the -3 but that’s not correct scientific notation because you have to have a value 1 or larger.

Move the decimal to the right one place (making the standard number larger) and make the exponent smaller to balance it out.

4 x 10 to the -4 power.