78 is the significant figure because in maths 0's are not considered significant. Read more into significant figures to help you out.
Short answer: the same way you do it with any other kind of numbers.
"Place value" means the value of a number comes from where it is (its place) in relation to the decimal point. The digit immediately to the left of the decimal point is the units digit, so tells you the number of units represented.
Each digit to the left of the units digit has a place value that is 10 times that of the digit to its right. Each digit to the right of the units digit (hence to the right of the decimal point) has a place value that is 1/10 that of the digit to its left.
The places have names (see attached).
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You can find the place value of a digit by setting all the other digits in the number to zero. For example, the place value of 2 in the number 324 is 020, or 20.

27mi/60min=9/20
9mi/20min=xmi/1min
Cross multiply
Divide by 20 on both sides
<span>x= 9/20
</span>
The process works well for a cylinder. It will not work for any other 3-D figures.
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I haven't needed to use a method, so there is no comparison.
If you are asked to find the area and volume, then the area/volume ratio, usually you will do it in that order. The "shortcut" is only useful if you don't need either volume or surface area as part of the answer to the question.
Answer:
After factoring we get:

Step-by-step explanation:
The expression given is:

We need to factor the expression using the formula:

Given the expression:
we have

Now applying the formula:

So, after factoring we get:
