The 5th term of an A.P. is −3 and its common difference is −4. The sum of its first 10 terms is :
−50
−40
−60
−30
AP
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Question

The 5th term of an A.P. is −3 and its common difference is −4. The sum of its first 10 terms is : 1. −50 2. −40 3. −60 4. −30

KnowledgeBoat · Accepted Answer

Given, a5 = -3 d = -4 n = 10 We know that, ⇒ an = a + (n - 1)d ⇒ a5 = a + (5 - 1)(-4) ⇒ -3 = a + (4)(-4) ⇒ -3 = a - 16 ⇒ a = 16 - 3 ⇒ a = 13. We know that, ⇒ Sn = [2a + (n - 1)d] ⇒ S10 = [2(13) + (10 - 1)(-4)] = 5[26 + (9)(-4)] = 5[26 - 36] = 5(-10) = -50. Hence, option 1 is the correct option.

Mathematics

The 5th term of an A.P. is −3 and its common difference is −4. The sum of its first 10 terms is :
−50
−40
−60
−30

AP

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Mathematics

The 5th term of an A.P. is −3 and its common difference is −4. The sum of its first 10 terms is :−50−40−60−30

AP

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The 5th term of an A.P. is −3 and its common difference is −4. The sum of its first 10 terms is :
−50
−40
−60
−30

There are total 9 terms in an A.P. If the last term and the sum of all the terms are 28 and 144 respectively, then the first term is :
1
7
4
5

The 7th term of an A.P. is −1 and its 16th term is 17. The nth term of the A.P. is :
(3n + 12)
(2n − 5)
(3n + 5)
(2n − 15)

If the sum of first p terms of an A.P. is ap² + bp, then its common difference is :
a
3a + b
a + b
2a