9 times the 9th term of an A.P. is equal to 11 times the 11th term , then its 20th term is
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Step-by-step explanation:
A9 = a+ 8d - equation 1
A11 = a + 10d -equation 2
9* A9 = 11* A11 -equation 3
9*(a+ 8d) = 11*(a + 10d)
9a + 72d = 11a + 110d
-2a = 38d
a = -19d
A20 = a+ 19d
A20 = -19d + 19d
A20 =0
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Answer: the real Question is this ...
If 9 times of 9th term of an AP is equal to 11 times of its 11th term then find 20 times its 20th term
A9 = a+ 8d - equation 1
A11 = a + 10d -equation 2
9* A9 = 11* A11 -equation 3
9*(a+ 8d) = 11*(a + 10d)
9a + 72d = 11a + 110d
-2a = 38d
a = -19d
A20 = a+ 19d
A20 = -19d + 19d
A20 =0
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