Question

(2.5×10−8)(9×10−10) Express your answer in scientific notation.

Answer 1

We have given expression as

$(2.5*10^{-8})(9*10^{-10}$

Now we can multiply 2.5 and 9 and also combine exponents of 10.

$(2.5*10^{-8}) * (9*10^{-10}) = 2.5*9 * 10^{-8-10}$
                                                  = $22.5*10^{-18}$

Now for writing it into scientific notation we have to shift decimal by one place in backward direction.
So we can write answer as

$22.5*10^{-18} = 2.25*10^{-18}* 10 = 2.25*10^{-17}$

So answer is $2.25*10^{-17}$

Answer 2

Answer: 2.25x $10^{-17}$

Scientific notation is used in science because the number can be vary from so much that using decimal is making it hard. The number expressed in $10^{x}$ form. Both number in the question is already in scientific notation. Then to multiply the number and keep it at scienfitic notation the calculation should be:

2.5 x $10^{-8}$x 9 x $10^{-10}$= 22.5 x $10^{-18}$= 2.25x $10^{-17}$