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Joshuafranklindude
28.05.2020 •
Mathematics
There are 90 counters in a bag. each counter in the bag are either red or blue.
The number of red counters : The number of blue counters = 2:13
Lee is going to put some more red counters in the bag so that the probability of taking at random a red counter from the bag is 1/3. Work out the number of red counters that Lee is going to put in the bag?
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Ответ:
27 red counters must be added
Step-by-step explanation:
If we know that for 2 reds there are 13 blues, this adds up to 15, now, to calculate how many there are of each would be:
90/15 = 6
Which means that there are 2 * 6 = 12 red and 13 * 6 = 78 blue.
Therefore, the probability that it is currently red is:
12/90
We need to get to 1/3, to get to this value, we must add an x quantity x:
12 + x / 90 + x = 1/3
3 * 12 + 3 * x = 90 + x
3 * x - x = 90 - 36
2 * x = 54
x = 54/2
x = 27
we try:
(12 + 27) / (90 + 27) = 39/117 = 1/3
Therefore 27 red counters must be added
Ответ: