Question

Multiply (2.5x10^-10) (7x10^-6)

Answer 1

The anwer will be 1.75*10^-15

Answer 2

We want to multiply $2.5\cdot10^{-10}$ by $7\cdot10^{-6}$.

The numbers are written in scientific notation. So we expect the answer also to be in scientific notation.

the multiplication of the 10's, using the exponents rule is :

$10^{-10}\cdot 10^{-6}=10^{-10+(-6)}=10^{-10-6}=10^{-16}$

the multiplication of the other 2 numbers is:

$2.5\cdot7=17.5=1.75\cdot10$

(we write the number so that it has only one digit to the left of the decimal point).

Thus, 

$(2.5\cdot10^{-10})\cdot(7\cdot10^{-6})=1.75\cdot10\cdot10^{-16}=1.75\cdot10^{-15}$



Answer: $1.75\cdot10^{-15}$