The number 3.07 × 10 -4 written in standard form is . 0.00307
0.000307
30,700
300,700

0.000307

Step-by-step explanation:

The first step I do when figuring out these type of questions is finding out which way we're going to be moving our decimal; Right or left?

We can quickly find out the answer by looking at whether the index is positive or negative. The index is the small number just next to the 10.

In this case, the index is negative. We can tell by the minus sign in front of it, which means it's a negative number. When the index is a negative, it means you're going to be moving your decimal to the right, AKA your number is going to get smaller.

Now all we need to know is how many spaces to the right the decimal needs to move. Again, this answer comes from the index. The number written in as the index is -4. We already know what the - means, so we can just look at the number as 4 on its own.

The index tells us that the decimal needs to be moved 4 places to the right. So that's just what we do!

3.07 ↓

0.307 ↓

0.0307 ↓

0.00307 ↓

0.000307

Moving the decimal 4 places to the right gives us the number 0.000307, which means;

The number × written in standard form is Option B, 0.000307.

lockers 1, 4, 9, 16, 25, 40, and 49 are open

i ran through it by the other answer is wrong