The ratio of 11th term to 18th term of an A.P. is 2:3 .Find ratio of 5th term to 21st term and also ratio of sum of first 5 terms to sum of first 21 terms
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Given t11: t18= 2 : 3
⇒ 3a + 30d = 2a + 34d
∴ a = 4d → (1)
Consider, t5: t25= (a + 4d) : (a + 24d)
= (4d + 4d) : (4d + 24d)
= 8d : 28d = 2 : 7
Hence ratio of 5thterm to the 21stterm is 2:7
Consider S5: S21
Therefore S5: S21= 5:49
HOPE IT HELPS YOU......
⇒ 3a + 30d = 2a + 34d
∴ a = 4d → (1)
Consider, t5: t25= (a + 4d) : (a + 24d)
= (4d + 4d) : (4d + 24d)
= 8d : 28d = 2 : 7
Hence ratio of 5thterm to the 21stterm is 2:7
Consider S5: S21
Therefore S5: S21= 5:49
HOPE IT HELPS YOU......
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