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प्रश्न
If the 2nd term of an AP is 13 and the 5th term is 25, what is its 7th term?
विकल्प
30
33
37
38
उत्तर
33
Explanation:
We know that the nth term of an AP is
an = a + (n – 1)d
Where,
a = first term
an is nth term
d is the common difference
a2 = a + d = 13 ...(1)
a5 = a + 4d = 25 ...(2)
From equation (1) we have,
a = 13 – d
Using this in equation (2), we have
13 – d + 4d = 25
13 + 3d = 25
3d = 12
d = 4
a = 13 – 4 = 9
a7 = a + 6d
= 9 + 6(4)
= 9 + 24
= 33
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