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Provide solution for RD Sharma maths class 12 chapter Probability exercise 30.7 question 30

Answers (1)

Answer:

 \frac{81}{85}

Hint:

Use Baye’s theorem. 

Given:

 If machine is correctly set up it produce 90% acceptable item. If it incorrectly set up the produce 40% acceptable item. Past experience show 80% of setup is correctly done. If after certain set up the machine produce 2 acceptance items.

Solution:

Let A be event that machine produce 2 acceptable item.

E1  Represents event of correct setup.

E2  Represents event of incorrect setup.

\begin{aligned} &P(E_1)=0.8\\ &P(E_2)=0.2\\ &P\left ( \frac{A}{E_1} \right )=0.9\times 0.9\\ &P\left ( \frac{A}{E_2} \right )=0.4\times 0.4\\ \end{aligned}

Using Baye’s theorem we get

\begin{aligned} &P\left (\frac{E_2}{A} \right )=\frac{P(E_2).P\left ( \frac{A}{E_2} \right )}{P(E_1)\times P\left ( \frac{A}{E_1} \right )+P(E_2)\times P\left ( \frac{A}{E_2} \right )}\\ &=\frac{{\frac{8}{10}\times \frac{81}{100} }}{\frac{8}{10}\times \frac{81}{100}+\frac{2}{10}\times \frac{16}{100}}\\ &=\frac{648}{680}\\ &=\frac{81}{85} \end{aligned}

Posted by

Gurleen Kaur

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