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Arithmetic Progressions
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01/06/2021 11:52 am
Topic starter
In an AP
(i) Given a = 3, n = 8, S = 192, find d.
(ii) Given l = 28, S = 144 and there are total 9 terms.
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01/06/2021 11:54 am
(i) Given that, first term, a = 3,
Number of terms, n = 8
And sum of n terms, S = 192
As we know,
Sn = n/2 [2a+(n -1)d]
192 = 8/2 [2×3+(8 -1)d]
192 = 4[6 +7d]
48 = 6+7d
42 = 7d
d = 6
(ii) Given that, l = 28, S = 144 and
there are total of 9 terms.
Sum of n terms formula,
Sn = n/2 (a + l)
144 = 9/2(a+28)
(16)×(2) = a+28
32 = a+28
a = 4