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bekas
11 days ago
9

A series contains 18 numbers and has a sum of 4,185. The last number of the series is 275. What is the first number?

Mathematics
1 answer:
Inessa [9K]11 days ago
3 0
The formula for the sum of an arithmetic series is expressed as:
Sn=n/2(a1+an)
where:
n=total terms
a1=the initial term
an=the final term
given
n=18, an=275, Sn=4185
substituting these values into the equation results in:
4185=18/2(a1+275)
after simplification, we obtain:
4185=9(a1+275)
dividing by 9 yields:
465=a1+275
therefore
a1=465-275
a1=190

Conclusion: the first term is 190
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6 0
1 month ago
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Add and simplify 9/16=1/2=what
zzz [9080]
9 / 16 + 1/2 =?

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(1 * 8) / (2 * 8) = 8 / 16

Step 2.  Add the numerators over the common denominator.

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Answer:

Step-by-step explanation:

Hello!

To determine whether boys excel in math classes compared to girls, two random samples were collected:

Sample 1

X₁: score achieved by a boy in calculus

n₁= 15

X[bar]₁= 82.3%

S₁= 5.6%

Sample 2

X₂: score obtained by a girl in calculus

n₂= 12

X[bar]₂= 81.2%

S₂= 6.7%

To estimate a confidence interval for the difference between the average percentages of boys and girls in calculus, it's essential that both variables come from normally distributed populations.

For utilizing a pooled variance t-test, it is also required that the population variances, though unknown, are assumed to be equal.

The confidence interval can then be calculated with:

[(X[bar]_1 - X[bar]₂) ± t_{n_1+n_2-2;1-\alpha /2} * Sa*\sqrt{\frac{1}{n_1} +\frac{1}{n_2} }]

Sa= \sqrt{\frac{(n_1-1)S^2_1+(n_2-1)S^2_2}{n_1+n_2-2} } = \sqrt{\frac{14*(5.6^2)+11*(6.7^2)}{15+12-2} }= 6.108= 6.11

t_{n_1+n_2-2;1-\alpha /2}= t_{15+12-2;1-0.05}= t_{25;0.95}= 1.708

[(82.3 - 81.2) ± 1.708 * (6.11 * \sqrt{\frac{1}{15}+\frac{1}{12} }]

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Using a 90% confidence level, the interval [-2.94; 5.14] is expected to encompass the true difference between the average percentages achieved by boys and girls in calculus.

I hope this is of assistance!

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Answer:

The illustration provided shows the graph

Step-by-step explanation:

Let

x ------> number of times Emma cuts the grass

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The solution is the shaded region above the solid line where both x and y are positive

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therefore

The illustration provided shows the graph

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