If the 20th term of an AP is five times its third term . If its 10th term is 41, then find the sum of its first fifteen term
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apis a,a+d,a+2d,a+3d
a+19d=5(a+2d)
4a-9d=0
a+9d=41
5a=41
a=41/5
d=41*4/9
sum of 15 term is 15/2(41/5+14*164/9)
444.166
a+19d=5(a+2d)
4a-9d=0
a+9d=41
5a=41
a=41/5
d=41*4/9
sum of 15 term is 15/2(41/5+14*164/9)
444.166
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