the fifth term of an ap is 20.the sum of fifth and seventh terms of the ap is 64.find the common difference.
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Answer:
d = 12
Step-by-step explanation:
nth term of an A.P = a+(n-1)d
5th term = a+(5-1)d = a+4d = 20-----(1)
Sum of n terms of an A.P =n/2{2a+(n-1)d
Sum of 5th and 7th term of A.P = 64
= a+(5-1)d + a+(7-1)d = 64
= a+4d+a+6d =64
= 2a + 10d = 64
Cancelling 2 from both the sides =
a+5d = 32---(2)
Subtracting eq(2) from eq(1)
a+5d = 32
-(a+4d = 20)
------------
d = 12
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