Re: In the flowchart, each rectangular box represents a distinct stage in
[#permalink]
20 Sep 2012, 01:55
If we translate the statement "Three quarters of all batches do not require additional heating" to the probability as following: 3/4 of a batch requires 0 heating and 1/4 of a batch requires 1 heating (worth 20 mins), and "half of all batches require a second mixing with hydrochloric acid, none requires the third" as 1/2 of a batch requires 1 mixing (20 mins) and 1/2 batch requires 2 mixing (40 minutes), the calculation for average time is as following:
30 mins + (3/4*0 +1/2* 20 mins) + 5 mins + (1/2 *20 mins+1/2 * 40 mins)+10+60 = 140 mins
For the stage, we count 1 for the rectangular box, the calculation will be 1+(3/4*0+1/4*1)+1+(1/2*1+1/2*2)+1+1 = 5.75.