One way to represent percentage is using decimal number. In this way, 1 is equivalent to 100% and the other less percentages using numbers between 0 and 1.

Examples:

90% is equivalent to 0,90.
5% is equivalent to 0.05. It's not 0.5 because 0.5 is equivalent to 50%.
13.17% is equivalent to 0.1317.
245% is equivalent to 2.45.

If we want to know the percentage of a number, we should multiplacate the number by the porcentage in the decimal number form.

Examples:

55.90% of 200 is equal to: $200 \times 0.5590 = 111.8$

360% of 88 is equal to: $88\times 3.6 = 316.8$

In our problem, we have a phone with a increase of 7%. To solve that, it's important to perceive that $230 is equal to 100% and with a increase of 7%, we will pay 107%.

107% in the decimal number form is 1.07. With that information, we should multiplicate 1.07 by the original value and we will find the answer.

We know that $230\times 1.07 = 246.1$ , therefore, the total cost of the phone after tax is $246.1.

I hope I've helped. :D

Enjoy your studies. \o/

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3 years ago