Determine the AP whose sum of 5th and 9th termsis 30 and 25th term is three times its 18th term
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erm is three times its 8th term find the ap
Report by Siladas8431 10.09.2017
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prmkulk1978
Prmkulk1978Brainly Guru
Solution:
Given sum of 5th term and 9th term of AP=30
a+4d + a+8d =30
2a + 12 d = 30 ---equation (1)
Given that 25 term is three times of 3rd term in AP
25th term= 3 (8th term)
( a+ 24d)= 3(a +7d)
a+ 24d = 3a+ 21d
24d - 21 d= 3a- a
3d = 2a --- equation 2
Substitute the value of 2d in equation (1) we get
2a+ 12d = 30
3d +12d =30
15d =30
d = 2
2a = 3d
2a= 3x 2
2a= 6
a=3
hence A.P. will be 3,5,7,9.....
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