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Question Video: Solving Word Problems Involving Percentages Mathematics • 7th Grade

Determine, to the nearest cent, the total price of an inflatable dolphin that costs $5.09 if the sales tax is 4.25%.


Video Transcript

Determine, to the nearest cent, the total price of an inflatable dolphin that costs five dollars and nine if the sales tax is 4.25 percent.

So, what we do first is rewrite the question so we can see exactly what we’re asked to do. And that is increase five dollars and nine by 4.25 percent. So, if we want to work out the total price of our inflatable dolphin, what we want to do is add on 4.25 percent. And we can do this using the multiplier method. And the multiplier for an increase of 4.25 percent is gonna be 1.0425. But how do we get this?

Well, there’re a couple ways of thinking about it. The first is if we think about the whole amount, that’s 100 percent. And if we want to increase it by 4.25 percent, we’re gonna have 100 percent plus 4.25 percent, which is 104.25 percent. And to have a multiplier, what we want to do is convert it into a decimal. So, as percent means out of 100, or by the 100, we can divide this by 100, which is gonna give us 1.0425. So, that’s one way of finding out what the multiplier would be.

The other way of considering the multiplier is to think that one is gonna be the whole of something. And then, we’re gonna add 4.25 percent to it, which is gonna be one add 4.25 over 100. And that’s because 4.25 over 100 will give us it as a decimal, which would give us one plus 0.425, which, once again, would give us our multiplier of 1.0425. Okay, great, so now we’ve got our multiplier, we can calculate the value of this question.

So, what we do to calculate the total price after the sales tax is multiply 5.09 by 1.0425, which is gonna be equal to 5.306325 dollars. Well, have we finished there? Well, not quite because the question asked us to leave it to the nearest cent. Well, if we round to the nearest cent, we’re gonna look at the second decimal place. So, then, we can see the digit that’s to the right of this, which is a six. Because it’s five or above, we round the zero to a one. So, we get five dollars and 31 cents.

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