# Help with probability problems

Updated on December 17, 2012

## Probability

Here in this hub i will offer you help with probability questions . By going through a few questions with you and explaining step by step reasons and workings i hope that this hub assists you in understanding probability better, and anwering problems with probability easier.

When we say probability, we refer to the likelyhood of an event to occur. There are a whole lot of questions we can ask about probability so lets get to it. One question which can be asked about probabilty is "What is the probabilty of a coin to land on heads when tossed into the air?" Ok we know that a coin has two sides and we know that it could either land on heads or tails. Therefore the answer to that question is ½.

Probabilty questions can either come in the form of a table, worded questions or in a probability tree diagram. A probability tree diagram represents all the possible situations based on a question. N.b each branch must add up to 1.

When doing probability questions you should know these two formulas which would surely assist you :

One for mutually exclusive, this is two or more events which cannot occur at the same time. The formula for this is P(A U B) =P(A) + P(B) .

The other formula is for conditional probability, this is the probability that an event will occur given that more than one event have occurred. Formula is P(A/B) =P (A ∩ B) over P(B).

## Lets answer probabilty problems from a table.

We'll answer the questions from the table above. For I, we see that the total number of females is 94 and the total number of children is 200. Therefore the answer for I is 94/200.

To the next question, it asks what is the probability that a randomly choosen kid prefers art. Ok looking at the table we see that 96 people prefer art and we know that the total number of kids is 200. The answer to II , is 96/200.

Next question asks the probability that the kid is a female and prefers games. This question is somewhat easy . The aswer is 44/200. Just go across from females and stop write under games and that's your answer.

Question 5. There are 46 kids who are male and prefer art. The question says given that this kids is a male, so the answer would have to be 46 over the total number of male. The answer is 46/106.

## Lets answer the probability tree questions

N.B.Remember that each branch is supposed to be equal to 1. A branch is a < looking object.

To calculate H. Since a branch is equal to 1 . To find H, subtract 0.4 from 1. The answer is then 0.6.

i) since you want to know the probability that she arrives early, you must find out the probability that she arrives early in both cases. So the probabilty that she gets home early using route A= 0.4 × 0.25 and the probability that she gets to work early using B is 0.6 × 0.4. Then add the two results together because in both cases she would get to work early. So the answer is 0.34.

ii)Travells by route A and arrives early. To answer this question we multiply 0.4 × 0.25, because route A is 0.4 and and to get work early by route A is 0.25.

## Question 3

The answer to this question is 1/6 because. The dice has six sides which are marked: 1, 2, 3, 4, 5, 6. In that bunch of numbers there is only one one. That is why 1 over 6 is the answer.

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• luvincent60@yahoo.com

8 years ago

A drug tester claims that a drug cures a rare skin disease 72% of the time. The claim is checked by testing the drug on 100 patients. If at least 65 patients are cured, the claim will be accepted. Find the probability that the claim will be rejected assuming that the manufacturer's claim is true.

• AUTHOR

mathslover

It was intended to help persons who have been taught probability but didn't quite understand by going through some questions.

10 years ago

that didn't teach me anything

• AUTHOR

mathslover