Question

radius of 11th term of A.P to it's 18th term is 2:3. find radius of sum of 5.term to sum of 15 term​

Answer 1

Answer:

Ratio = 2:11

Step-by-step explanation:

Let the first term of the AP be a

and common difference be d.

$So, \frac{a + 10d}{a + 17d} = \frac{2}{3} \\ = > 3a + 30d = 2a + 34d \\ = > a = 4d$

$So, Ratio = \frac{ \frac{5}{2}(2a + 4d) }{ \frac{15}{2}(2a + 14d)} \\ = \frac{1}{3} \times \frac{(a + 2d)}{(a + 7d)} \\ = \frac{1}{3} \times \frac{4d + 2d}{4d + 7d} \\ = \frac{1}{3} \times \frac{6}{11} \\ = \frac{2}{11} \\ =2:11$

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