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Q.

State True/False.


If the sum of the first 14 terms of an AP is 1505 and the first term of an AP is 10, then 25th term is 370.


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a

True

b

False 

answer is A.

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Detailed Solution

Given that the sum of 14 term is 1505.
S 14 =1505
Let the first term be a and common difference be d.
a = 10
Formula used for sum of first n term of A.P.:
S n = n 2 [2a+(n1)d]
Applying formula for sum of first n terms of A.P.:
  S 14 = 14 2 [2(10)+(141)d] 1505=7[20+(13)d] 215=20+13d 13d=195 d=15
Therefore, the common difference is 15.
Formula for the n th term:
a n =a+ n1 ×d
So, the 25th term of the A.P. is:
a 25 =10+(251)15 a 25 =10+(24)15 =10+360 =370
Therefore, 25 th   term of the A.P. is 370 
Thus, the given statement is true.
Hence, option (1) is correct.
 
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