Makky07 wrote:

Another way you could solve this:

Say 100(divisible by all the denominators mentioned) light switches are produced.

1/5 * 100 = 20 defective leaving 80 non-defective

4/5 * 20 defective = 16 rejected leaving 4 non-rejects defectives

1/20 * 80 non-defective = 4 rejected non-defectives

so 80 non-rejects are sold and 4 are defective

4/80 = 0.05 = 5%

small elaboration. i was slightly confused by the wording and took the total defective amount rather than the defective amount of the units sold.

If all the switches not rejected are sold, what percent of the switches sold by the factory are defective?

4 / (4 + 76)

4/80

1/20

5%

B