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ikadub [295]
2 years ago
13

50 students each did a mathematics test. the mean score for these 50 students was 8.4. there were 30 boys. the mean score for th

ese bots were 8.25. workout the mean score for the girls.
Mathematics
1 answer:
Angelina_Jolie [31]2 years ago
7 0

[(30 x 8,25) + (20 x n)] / 50 = 8,4

247,5 + 20 x n = 420

n = (420 - 247,5) : 20

n = 8,625

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Answer:

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Step-by-step explanation:

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if we have the summation between k = 0 and k = ∞ - 1 = ∞

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In the numerator we will have the term r^∞, if 0 < r < 1, then r^∞ = 0.

Then if we assume that 0 < r < 1 we can write:

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In our case, we can rewrite our summation as:

3*∑ (1/2)^n

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You can see that i changed the limits for n, this does not really matter because we are summing between a number and infinity, the only thing you need to take care is that now the power is n, instead of (n - 1)

Then we have r = (1/2) which is clearly smaller than 1.

then (1/2)

Then this summation is equal to:

3*∑ (1/2)^n = 3*( 1/(1 - 1/2)) = 3*( 1/( 2/2 - 1/2)) = 3*( 1/(1/2)) = 3*2 = 6

3*∑ (1/2)^n = 6

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