Data Sufficiency

In 1995 Division A of company X had 4850 customers. If there were 86 service errors in Division A that year, what was the service-error rate, in number of service errors per 100 customers for Division B of Company X in 1995?

1. In 1995 the overall service-error rate for Divisions A and B combined was 1.5 service errors per customers.

2. In 1995 Division B had 9350 customers, none of whome were customers of Division A.

let B be the number of customers in B division and number of faults be x.

thus

a total faults = 86+x total customers = 4850+B

hence (86+x)/(4850+B) = 1.5. two variables and 1 equation. cannot be solved. not sufficient.

b B = 9350. but still we dont have x. not sufficient.

a+b

(86+x)/ (4850+9350) = 1.5 gives x and hence can be calculated for 100 customers for B.

thus C it is.