What is the product written in scientific notation?

(2.1 x 10-2) (3.2 x 10-4)

a. 6.72 x 108

b. 6.72 x 10-6

c. 5.3 x 102

d. 5.3 x 10-6

First, you multiply 2.1 by 3.2, which gives you the answer of 6.72. Then, you multiply 10-2 by 10-4. One rule about multiplying exponents, you just add the exponents. So 10-2 x 10-4 = 10-6. Finally you get the answer of C. 6.72 x 10-6.