Question

simplify the expression. write the answer using scientific notation. (9x10^7)(7x10^9) 1.6x10^17 1.6x10^64 6.3x10^64 6.3x10^17

Answer 1

`The\ scientific\ notation:a\cdot10^n\ where\ 1\leq a \ \textless \ 10\ and\ n\in\mathbb{Z}\\----------------------------\\\\(9\cdot10^7)(7\cdot10^9)=(9\cdot7)(10^7\cdot10^9)=63\cdot10^(7+9)\\\\=63\cdot10^(16)=6.3\cdot10^(16+1)=6.3\cdot10^(17)`

Answer 2

`6.3*10^(17)`

Explanation:

We have to multiply the expression

`(9*10^7)*(7*10^9)`

We can rewrite this multiplication as

`(9*7(10^7*10^9)`

Now, use the exponent rule,
`x^a\cdot x^b=a^(a+b)`

`63*10^(7+9)\\\\=63*10^(16)`

Finally, write in scientific notation

`6.3*10^(17)`

Last option is correct.