Question

Question :-

Find the sum of the AP whose First term (t1) is 5,common difference (d) is 5 and Last term (tn) is 100.
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Answer 1

Answer:

Question :-

Find the sum of the AP whose First term (t1) is 5,common difference (d) is 5 and Last term (tn) is 100.

Required Answer :-

We know that,

tn = a + (n - 1)d - [formula]

100 = 5 + (n - 1) x (5)

100 - 5 = (n - 1) x (5)

95/5 = n - 1

13 = n - 1

13 + 1 = n

n = 14

Now,

Sn = n/2 x [2a + (n - 1)d]

S¹⁴ = 14/2 x [2(5) + (14 - 1) x (5)]

S¹⁴ = 7 x [10 + 13 x 5]

S¹⁴ = 7 x 75

S¹⁴ = 525

Hope it help you :)

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