Question: Choose the correct choice in the following and justify:
i. 30th term of the AP: 10, 7, 4, ....., is
- 28
- 77
- -77
- -87
- 28
- 22
- -38
- -48\\frac{1}{2})
Explanatory Answer
i. 30th term of the AP: 10, 7, 4, …., is
The given AP is 10, 7, 4,.....
a = 10, d = -3, n = 30
an = a + (n – 1)d
an = 10 + (30 – 1) × -3
an = 10 + 29 × -3
an = -77
Choice C
ii. 11th term of the AP: -3, -\\frac{1}{2}), 2, ....., is
The given AP is -3, -\\frac{1}{2}), 2, .....
a = -3, d = 2.5, n = 11, an = ?
an = a + (n - 1) d
an = -3 + (11 – 1) × 2.5
an = -3 + 25 = 22
Choice B