percentage math problem

[djv1087]

Hello,
I am looking to create a formula to solve the following word problem:

I have a store that receives good or bad customer reviews. A review can be either good or bad. The goal is to reach 66% good reviews. I want to be able to determine how many more good reviews are needed to reach 66% good.

For example, if I have a total of 2 reviews - one bad, one good - I'm at 50% good reviews. In order to reach 66% good reviews I would need one more good review (there would be a total of 3 reviews now, two of which are good).

Could someone help develop this into a formula that I could ultimately utilize in Excel?

Thanks,
DJV

 

[stapel]

I have a store that receives good or bad customer reviews. A review can be either good or bad. The goal is to reach 66% good reviews. I want to be able to determine how many more good reviews are needed to reach 66% good.

For example, if I have a total of 2 reviews - one bad, one good - I'm at 50% good reviews. In order to reach 66% good reviews I would need one more good review (there would be a total of 3 reviews now, two of which are good).

You are working with two changing values, so assign variables; say, "p" for "positive" and "n" for "negative. These variables will hold the counts for the types of reviews.

What expression then stands for the total number of reviews? (here)

You are wanting to find the percentage of reviews which are positive. What expression stands for this percentage (as a decimal)?

You have a fixed minimum for this percentage; you want the value to be greater than or equal to 2/3 (in fractional form). What inequality can you create from this?ds

If the inequality is true, then you have a sufficient number of positive reviews. If it is not true, then you can leave the value of "n" fixed, and solve the inequality to find the necessary value for "p". Subtract this from the present value of "p" to find the additional positive reviews needed.

If you get stuck, please reply showing your progress so far. Thank you!