-
Only two entries are known of the following Arithmetic progression : ––, 5, ––, ––, 14, ––, --What should be the number just after 14 ?
-
- 17
- 18
- 19
- 20
- 17
Correct Option: A
For an arithmetic sequence,
tn = a + (n – 1) d
∴ 5 = a + (2 – 1) d
⇒ 5 = a + d .........(i)
and 14 = a + 4d ......(ii)
By subtracting equation (i) from (ii), 
| ∴ d = | = 3 | |
| 3 |
From equation (i),
5 = a + 3 ⇒ a = 5 – 3 = 2
∴ t6 = 2 + (6 – 1) × 3
t6 = 2 + 15 = 17
