If 18th and 11th term of an A.P. are in the ratio 3 : 2, then its 21st and 5th terms are in the ratio
A. 3: 2
B. 3: 1
C. 1 :3
D. 2 : 3
Answers
Answered by
24
B. 3: 1
Step-by-step explanation:
18th and 11th term of an A.P. are in the ratio 3 : 2, then its 21st and 5th terms are in the ratio.
a18 = a + 17d
a11 = a + 10d
Given a18: a11 :: 3:2
So 2(a18) = 3(a11)
2(a+17d) = 3(a+10d)
2a + 34d = 3a +30d
a - 4d = 0
a = 4d --------(1)
a21 = a + 20d
a5 = a + 4d
Hence a21/a5 = a+20d / a+4d = 4d+20d / 4d+4d = 24/8 = 3:1
Option B is the answer.
Answered by
8
Answer:
(b) 3:1
Step-by-step explanation:
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