Home Opt. Mathematics Q. If 7 times the 7th term of an AP is equal to 11 times its eleventh term, show that the 18th term of the AP is zero.

Saturday, July 15, 2017

Q. If 7 times the 7th term of an AP is equal to 11 times its eleventh term, show that the 18th term of the AP is zero.

Soln:
Let first term = a and common difference = d in the AP.
We have, nth term
tn = a + (n -- 1)d
Seventh term (t7) = a + (7 - 1)d
t7 = a + 6d ..............(i)
Similarly,
11th  term (t11) = a + 10d............(ii)
It is given that,
7t7 = 11t11
7(a + 6d) = 11(a + 10d)
7a + 42d = 11a + 110d
11a - 7a = 42d - 110d
4a = -68d
a = -17d

Therefore, t18 = a + 17d = -17d + 17d = 0 
Q. If 7 times the 7th term of an AP is equal to 11 times its eleventh term, show that the 18th term of the AP is zero. Q. If 7 times the 7th term of an AP is equal to 11 times its eleventh term, show that the 18th term of the AP is zero. S.E.E. Solution 5.0 stars based on 35 reviews Soln: Let first term = a and common difference = d in the AP. We have, nth term tn = a + (n -- 1)d Seventh term (t7) = a + (7 - 1)d ...
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