MHB Probability of Order Accuracy from A, C, or Not Accurate

[jridgeman99]

This is a problem I got for a review in probability and statistics

The layout of the data is as follows:
A B C D
Order Accurate- 315 277 234 120
Order not - 34 50 35 18
accurate

Like I said previously this is an or problem and this means it is an addition rule problem. The problem wants me to compute
the probability that whenever a single order is selected what is the probability that this probability is from restaurant A or C or an order that is not accurate.
I know the answer is .633 I just can't figure out how to set up the problem.

 

[skeeter]

This is a problem I got for a review in probability and statistics

The layout of the data is as follows:
A B C D
Order Accurate- 315 277 234 120
Order not - 34 50 35 18
accurate

Like I said previously this is an or problem and this means it is an addition rule problem. The problem wants me to compute
the probability that whenever a single order is selected what is the probability that this probability is from restaurant A or C or an order that is not accurate.
I know the answer is .633 I just can't figure out how to set up the problem.

[(all A) + (all C) + (inaccurate B) + (inaccurate D)]/total

$\dfrac{(315+34)+(234+35)+50+18}{1083} = 0.6334$