In a stockpile of products produced by three machines M1, M2 and M3

In a stockpile of products produced by three machines M1, M2 and M3, 40% and 30% were manufactured by M1 and M2 respectively. 3% of the products of M1 are defective, 1% of products of M2 defective, while 95% of the products of M3 are not defective. What is the percentage of defective in the stockpile?

  1. 5%
  2. 4%
  3. 3%
  4. 2.5%

Answer

Let there be 100 products in the stockpile. 40% and 30% were manufactured by M1 and M2 respectively. So, 30% are manufactured by M3.

Products from M1 = 40, from M2 = 30 and from M3 = 30. 

Number of defective products from M1 = 0.03 x 40 = 1.2, from M2 = 0.01 x 30 = 0.3 and from M3 = 0.05 x 30 = 1.5

Therefore, total number of defective products = 3

The correct option is C.