I'll explain the problem in a nutshell.(adsbygoogle = window.adsbygoogle || []).push({});

2% of brand X tires are faulty, 98% aren't.

If you take a car with 4 brand X tires, what is the probability that 3 of them are faulty?

My work: (.02^3 * .98) * 4 = 0.003136%

However, my teacher thought it was just: (.02^3 * .98) = 0.000784%

I believe my teacher left out the combinations that the 3 tires could be in in 4 spaces. ( 4 combinations ) XXXO, XXOX, XOXX, OXXX.

Leaving this out is correct only if it specified which space the 3 faulty ones had to be in, no?

I mentioned this in class and got shot down by the teacher leaving me somewhat frustrated. Can someone else just confirm this? It would mean a lot.

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# Very simple question, believe teacher is wrong.

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