# How do you write 70 million in scientific notation?

Jun 16, 2015

$7 \cdot {10}^{7}$

You only need one significant figure because $70000000$ only has one significant figure.

Jun 23, 2015

The correct answer is $7 , 0 \setminus \cdot {10}^{7}$

#### Explanation:

For seeing this first of all you have to know about significant numers, you are SURE that your number is 70 millons so you are sure that it is 70 and not 71 nor 69, you know that the second digit is for sure a 0, if you say 7,010^7 you are telling me that you are sure that it is a 0 what follows the 7, if you say 710^7 you just know that the first numer is a 7 so it could be between 6,6/7,5 by saying it is 7.0 you are tellin, the numer is between 6.96/7.05 which is the information that you previously knew.

Now that you know that your significant numbers are 7,0 ( later i'll explain some exceptions) we have to look which power of ten this significant number need to be 70 millons.

As humans count in a decimal sistem ( computers work in binary code) its really easy for us to multiply by 10 the numers, you only have to move the coma.

By multipliying by 10 a numer for example your 7,0 you move the coma one position to the right so it becomes a 70, once again it would become 700 once more 7000, as you can see everytime you multiply by ten it moves on position (yeah once the coma is at the right we add a 0 instead of moving the coma, it's the same)

And if you count how many positions you have to move the coma from 7,0 to get the 70.000.000 you see that you move the coma one position to the right there's a ten and then you add 6 zeros so there you have 6 more tens. So you have ${10}^{7}$

So by multiplying $7 , 0 \setminus \cdot {10}^{7}$ is 70 millions

Sometimes you have to erase some significant numbers, there's no point insaying the speed of light is 299792458m/s and say it is 2,99792458·10^8 here for an aproximation you would say the speed of light is 3·10^8; 3,0·10^8; 2.9979·10^8 sometimes you have to cut some numbers following your own criteria, you should'nt use a really long number if you are using scientific notation