JEE Main 26 Feb 2021 Shift 2 Solved Paper

Let x be four digit number, then gCd(x,18)=3
This implies x is divisible by 3 but not divisible by 9 .
The 4-digit numbers which is an odd multiple of 3 are 1005,1011 , 1017,.....9999
These are 1499 in counting i.e. total number of 4-digit numbers which is odd multiple of 3 are 1499.
Now,
The 4-digit numbers which is an odd multiple of 9 are, 1017,1035 , ...9999
These, are total 499.
Then, required 4-digit numbers =1499−499=1000