Q. 5 . Let the number = N
So,
N = 10a9 + 9
= 9a8 + 8
= 8a7 + 7
= 7a6 + 6
… …
= 2a1 +1
⇒ N+1 = 10(a9+1)
= 2(a1+1)
i.e. N+1 is having 2,3,4,5, ….. 10 as a factor
Taking LEM of 2,3,4,5,….. 10
= 2520
∴ N = 2519
Q. 6. Suppose man went out at x minute past 3 pm and returned at 30+x minute past 3 pm.
The angle between hands of clock at time of leaving
The angle between hands when he comes back
