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Question
The sum of 25 terms of A.P. 8 + 12 + 16 + .... is ______.
Options
1400
1600
1800
2000
MCQ
Fill in the Blanks
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Solution
The sum of 25 terms of A.P. 8 + 12 + 16 + .... is 1400.
Explanation:
a = 8
d = 12 − 8
= 4
n = 25
`S_n = n/2[2a + (n - 1)d]`
`S_25 = 25/2[2(8) + (25 - 1)4]`
`S_25 = 25/2[16 + (24)4]`
`S_25 = 25/2[16 + 96]`
`S_25 = 25/2[112]`
S25 = 25 × 56
S25 = 1400
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