Question

An author has 4 typists typing the manuscript of his latest book. Typist
A does 30% of typing; Typist B 25%; Typist C 20% and Typist D 25%.
Errors occur on 5% of the pages typed by A; on 4% typed by B; on 3%
typed by C; and on 2% typed by D. A page is chosen at random and
found to contain errors. What is the probability that it was typed by
Typist A?​

Answer 1

total percent the all type 100%

Typist A type 30% and error is 5 %

then he type 25%

so probability is 25/100= 1/4