Question

Which proportion can be used to determine what number is 15% of 30? (1 point)
15/30 = x /100
15/100 = x/30
15/100 = 30/x
or 30/100 = 15/ x i just tried had no luck

Answer 1

When you read 15% what does that little % mean? It means "percent". It's really two words put together, "per" and "cent"

Per just means you're taking the first number and dividing by another number. For example, if you go fifty miles "per" hour then you could write it like this: \[\frac{ 50 miles }{ 1 hour }\]

So what does per "cent" means? Well, like I said in my explanation of "per", it's really just a number. How many years are in a "cent"ury? 100 years! How many pennies are in a dollar? 100 cents! Here it's no different, "cent" just means 100.

So now we know 15% is really \[\frac{ 15 }{ 100 }\]

Now we want to find out what 15% of 30 is. If we had 100% of 30, we'd just have 30 right? So we should expect that 15% is less than 30, so we set up our fraction so that it shows it as being a part of 30, with the unknown on top, just like you would have 5/6 of a cake left after you take a piece, not 6/5 since that's somehow magically gaining cake slices.