Correct Answer - Option 4 : 9
Concept:
The LCM of two or more given numbers is the least number which is exactly divisible by each of them.
Caclculation:
2
|
20, 24, 32, 40
|
2
|
10, 12, 16, 20
|
2
|
5, 6, 8, 10
|
2
|
5, 3, 4, 5
|
2
|
5, 3, 2, 5
|
3
|
5, 3, 1, 5
|
5
|
5, 1, 1, 5
|
|
1, 1, 1, 1
|
L.C.M. = 2 × 2 × 2 × 2 × 2 × 3 × 5 = 480
Given, x should be divisible by 9.
Let (480k + 9) is divisible by 9.
x = (480k + 9)
Put k = 1, 2, 3, 4, 5…..
(i) When, k = 1, x = 489 is not divisible by 9.
(ii) When, k = 2, x = 969 is not divisible by 9.
(iii) When, k = 3, x = 1449 is divisible by 9.
⇒ x = 1449
∴ The unit digit of x is 9.