Answer :

Answer:

6.3 × 10^ 15

Step-by-step explanation:

(2.1 x 10^6)(3 x 10^9)

= 2.1 × 3 × 10^6 × 10^9 Law of indices

= 6.3 × 10^(6+9)

= 6.3 × 10^ 15