The ratio of boys to girls in Ella's class is 2 to 5. There are 12 boys in Ella's class. How many girls are there? Answer value
2 answers:
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We need to determinate who doesn't use anything, so first we must know the real number of who are practising: a person can do more things.
For doing this, is better use a three-circles graphic, but we try to do without it.
So
- 16 pool + gym + track, and this number is sure
- 38 gym + pool, but this number includes the people of 1st point. We must know who do only gym + pool: 38 - 16 = 22
- 31 pool + track, this number also includes people of 1st point, so: only pool + track 31 - 16 = 15
- 33 gym + track, this number also includes people of 1st point, so: only gym + track 33 - 16 = 17
now:
- 67 gym, we must know who use only gym: 67 - 16 (gym + pool + track) - 22 (gym + pool) - 17 (gym + track) = 12
- 62 pool, we must know who use only pool: 62 - 16 (gym + pool + track) - 22 (gym + pool) - 15 (pool + track) = 9
- 56 track, we must know who use only track: 56 - 16 (gym + pool + track) - 15 (pool + track) - 17 (gym + track) = 8
now we must now who do some facility: let's sum all
16 + 22 + 15 + 17 + 12 + 9 + 8 = 99
99/100 practise something
So only 1/100 doesn't use nothing
The probability is 1%
Answer:
3.70% probability she allows more than one goal
Step-by-step explanation:
In a Poisson distribution, the probability that X represents the number of successes of a random variable is given by the following formula:
In which
x is the number of sucesses
e = 2.71828 is the Euler number
is the mean in the given time interval.
X~Pois(0.3)
This means that
In her next match, what is the probability she allows more than one goal?
Either she allows at most one goal, or she allows more than one goal. The sum of the probabilities of these events is decimal 1. So
We want . So
In which
3.70% probability she allows more than one goal