Question

In a bolt manufacturing factory, machines 4, Band C produce 25%, 30% and 45% of

the total output respectively, of their output, 7%, 6% and 4% are defective bolts,
respectively. A bolt is drawn at random from production, what is the probability that it
was found to be non-defective?
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Answer 1

In the first 25% of the produce, 7% of that is defective. Which means that 25%*93% is not defective.

=20.75% not defective.

In the second 30% of the produce, 6% is defective Which means that 30%*94%

=28.2% not defective

Now for the 3rd 45% of the produce, 4% is defective which means that

45%*96%

=43.2% not defective.

Added together, 20.75+28.2+43.2=92.15% not defective.