SOLUTION: a). In an AP, the first term -5 and the last term is 105. If the sum of these terms is 1550, how many terms are there in the AP?
b). The first three terms of a G.P are x+1, x+3 an
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-> SOLUTION: a). In an AP, the first term -5 and the last term is 105. If the sum of these terms is 1550, how many terms are there in the AP?
b). The first three terms of a G.P are x+1, x+3 an
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Question 1126795: a). In an AP, the first term -5 and the last term is 105. If the sum of these terms is 1550, how many terms are there in the AP?
b). The first three terms of a G.P are x+1, x+3 and x+8, and find
i) The value of x
ii) The common ratio
iii) The sum of the first 15 terms. Answer by ikleyn(52787) (Show Source):
The sum of the first n terms of an arithmetic progression (of any arithmetic progression) is
= .
This formula ideally suits to solve the given problem, since the terms and are given in the condition.
So, in your case
1550 = = = 50n,
which gives you the number of the terms n = = 31.
Answer. There are 31 terms in the given AP.
