A bag contains 3 red marbles and 4 blue marbles. A marble is taken at random from the bag and replaced. Another marble is taken from the bag. Work out the probability that the two marbles taken from the bag are the same colour
Answers
Answer:
25/49
Step-by-step explanation:
The total number of marbles in the bag is 3 (red marbles) + 4 (blue marbles) = 7.
If a marble is taken at random and then replaced, we still have seven marbles, so just keep the denominator the same for now.
It says same, so that's basically either red AND red OR blue AND blue.
AND rule and the OR rule in probability:
If the question outwardly states or implies AND, then you multiply the 2 calculated probabilities.
If the question outwardly states or implies OR, then you add the 2 calculated probabilities.
So, here, we have both of these rules.
Look: type this into you calculator EXACTLY AS IT IS HERE (3/7*3/7)+(4/7*4/7).
And you should get 25/49.
The reason why you should type this exactly as I've written it is because of BIDMAS. Go REALLY careful here.
If this is a non-calculator question, do this:
(a) 3/7 * 3/7 = 9/49 (multiply numerator by numerator and denominator by denominator, or basically 3x3 = 9 and 7x7 = 49).
(b) 4/7 * 4/7 = 16/49 (multiply numerator by numerator and denominator by denominator, or basically 4x4 = 16 and 7x7 = 49).
(c) And then do 9/49 + 16/49 = 25/49.
Notice how, for parts (a) and (b), we multiplied. Why? Because of the AND rule.
Notice how, for part (c), we added. Why? Because of the OR rule.
Either way, you should get 25/49. Good luck, student!
Answer:
25/49
Step-by-step explanation:
I can't lie my math teacher just gave me the answer, no clue how to do it but it's correct.