if 8th term of an A.P equal to 5times its second term if its 5th term is 18 find the sum of the first 10 terms
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8th term = 5 times of 2nd term
a+7d = 5(a+d)
a + 7d = 5a + 5d
4a = 2d
a = 0.5d
Also given
5th term = 18
a + 4d = 18
0.5d + 4d = 18 (Substituting a = 0.5d)
4.5d = 18
d = 4
So, a = 2
The AP is
2, 6, 10, 14, 18, 22, 26, 30, 34, 38,
a+7d = 5(a+d)
a + 7d = 5a + 5d
4a = 2d
a = 0.5d
Also given
5th term = 18
a + 4d = 18
0.5d + 4d = 18 (Substituting a = 0.5d)
4.5d = 18
d = 4
So, a = 2
The AP is
2, 6, 10, 14, 18, 22, 26, 30, 34, 38,
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