Question

Multiply (2.5 x 10 ^-8) ( 9x10 ^ - 10 ) Express answer in scientific notation

Answer 1

when you multiply scientific notation numbers add the exponents ( -8 + -10 = -18)

 now multiply 2.5 *9 = 22.5

 so you now have 22.5x10^-18

now make 22.5 a real scientific number by moving the decimal point 1 place to the right, which subtracts 1 from the exponent

 so you get:

2.25x10^-17

Answer 2

2.25 x 10^-17. Because it's negative you move the decimal to the left. So 2.5 x 10^-8 is .000000025 and 9 x 10^-10 is .0000000009.