The given numbers are `1,3,5,7.....99,`
This an A.P with a=1 and d =2.
Let it contain n terms.Then,
`1+(n-1) xx 2=99 or n=50.`
`:.`Required sum =`n/2 ("first terms" + "last terms")`
                       =`50/2 xx (1+99)=2500`.

All 2 digit numbers divisible by `3` are :

 `12,15,18,21,......99`.

 This is an A.P. with `a =12` and `d=3`.

 Let it contain n terms.Then,

 `12+(n-1) xx 3=99` or `n=30`.

 Required sum =`30/2 xx (12+99) = 1665`.

`= 12846 xx (593+407)`

 `= 12846 xx 1000`

 `= 12846000`

`=987 xx (1000-1)`
     ` =(987 xx 1000)-(987 xx 1)`
     ` =(987000-987)`
      ` =986013`

=4691570000-469157
 =4691100843