Q15 of 85 Page 110

If T4 = 7 and T7 = 4, then T10 = …..

Given T4 = 7


And we know that, Tn = a + (n – 1)d


So we have T4 = a + (4 – 1)d


7 = a + 3d …… (1)


Then, T7 = 4


T7 = a + (7 – 1)d


4 = a + 6d …….(2)


Now, (2) – (1) gives :


– 3 = 3d


d = – 1


so, now, putting value of d in (1),


7 = a + 3d


7 = a + 3( – 1)


7 = a – 3


a = 10


so now T10 = a + (10 – 1)d


T10 = a + 9d


= 10 + 9( – 1)


= 10 – 9


= 1


T10 = 1


correct option is (d)

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