How do you write $70$ million in scientific notation?

Hint: We know that a million contains six zeros. So, in that case, $10$ million contains a $10$ and six zeros. So, ten million contains a total of seven zeros. When we multiply a number with ten million, the product will contain seven zeros and the number at the leftmost side.

Complete step-by-step answer:
Let us consider the number $70$ million.
We need to write this number in the scientific notation. That means, we need to write the exponential form of the given number.
This number can be written as $7,00,00,000.$
Let us consider the fact that we multiply the nonzero digits first and then write as many zeros as the two numbers contain at the right end of the product when two numbers are multiplied.
From this we get, $7,00,00,000=70\times 1000000.$ Because, when we multiply $70$ and $1,$ we will get $70.$ Then we add six zeros at the right end.
In the same way, we can write it as $7,00,00,000=7\times 10000000.$
Now, we are going to recollect another fact. That is, $1,00,00,000$ can be written as the seventh power of $10.$ That is, $1,00,00,000={{10}^{7}}.$ Because the product of seven tens is ten million. That is, $10\times 10\times 10\times 10\times 10\times 10\times 10=1,00,00,000.$
So, we will get $7,00,00,000=70\times 1000000=70\times {{10}^{6}}.$
We know that $70=7\times 10.$ So, we will get $7,00,00,000=7\times 10\times {{10}^{6}}.$
That is, $7,00,00,000=7\times {{10}^{7}}.$
The above obtained is the exponential form of the given number. We know that the scientific notation of a number is its exponential form.
Hence the scientific notation of the given number is given by $7\times {{10}^{7}}.$

Note: We can write $70$ million as a product of $70$ and one million. That is $70\times 10,00,000.$ We can also write $70$ million as a product of $7$ and ten million. That is $7\times 1,00,00,000.$ We know that the scientific notation is the exponential form of a number.