Question

What is the product 2.5 x 10^-15 and 3.9 x 10^26

Answer 1

$\bf (2.5\times 10^{-15})(3.9\times 10^{26})\implies (2.5\cdot 3.9)\times (10^{-15}\cdot 10^{26}) \\\\\\ (9.75)\times (10^{-15+26})\implies (9.75)\times (10^{11})\implies 9.75\times 10^{11}$