# Math Help - Probability Word Problem

1. ## Probability Word Problem

I can't seem to come up with the correct answer. Any help would be appreciated. Thanks!

Problem: You ask a neighbor to water a sickly plant while you are on vacation. Without water, the plant will die with a probability of 90%. With water, it will die with a probability of 30%. You are 95% certain the neighbor will remember to water the plant. You come back from vacation and the plant is dead. What is the probability the neighbor forgot to water it?

2. Originally Posted by eri123
I can't seem to come up with the correct answer. Any help would be appreciated. Thanks!

Problem: You ask a neighbor to water a sickly plant while you are on vacation. Without water, the plant will die with a probability of 90%. With water, it will die with a probability of 30%. You are 95% certain the neighbor will remember to water the plant. You come back from vacation and the plant is dead. What is the probability the neighbor forgot to water it?
Draw a tree (hah! hah!) diagram and use Bayes Theorem:

$\frac{(0.05)(0.9)}{(0.05)(0.9) + (0.95)(0.3)} = ....$