Q2 of 110 Page 41

Find the common difference and 15th term of the A.P. 125, 120, 115, 110 …

The given A.P. is 125, 120, 115, 110 …


We know that common difference, d = a1 – a.


⇒ d = 120 – 125


= -5


∴ Common difference = -5


We know that nth term of A.P. , tn = a + (n – 1) d.


⇒ t15 = 125 + (15 – 1) (-5)


= 125 + 14 (-5)


= 125 – 70


= 55


∴ 15th term of A.P. = 55


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