What is a31 of the arithmetic sequence for which a5=12.4 and a9=22.4
1 answer:
For the arithmetic sequence
a₁, a₂, a₃, ...,
the n-th term is
where d = the common difference
Because a₅ = 12.4,
a₁ + 4d = 12.4 (1)
Because a₉ = 22.4,
a₁ + 8d = 22.4 (2)
Subtract (1) from (2).
a₁ + 8d - (a₁ + 4d) = 22.4 - 12.4
4d = 10
d = 2.5
From (1),
a₁ = 12.4 - 4*2.5 = 2.4
Therefore
a₃₁ = 2.4 + 30*2.5 = 77.4
Answer: a₃₁ = 77.4
a₁, a₂, a₃, ...,
the n-th term is
where d = the common difference
Because a₅ = 12.4,
a₁ + 4d = 12.4 (1)
Because a₉ = 22.4,
a₁ + 8d = 22.4 (2)
Subtract (1) from (2).
a₁ + 8d - (a₁ + 4d) = 22.4 - 12.4
4d = 10
d = 2.5
From (1),
a₁ = 12.4 - 4*2.5 = 2.4
Therefore
a₃₁ = 2.4 + 30*2.5 = 77.4
Answer: a₃₁ = 77.4
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The value that is greater than 45% of the data values is approximately 137.84.
Step-by-step explanation:
The key is transforming values from this distribution to a z-score range and finding the corresponding value using a z-score table.
We are looking for a value x which attains a critical z-score that corresponds to the (100-45)%=55-th percentile:
The critical z value (from z-score table, online) is: -0.12, so:
The value that is greater than 45% of the data values is approximately 137.84.