Q) If f(x) is sum of all digits of x then find f(101) + f(102) + f(103) .... f(200) .

A)
f(101) + f(102) + f(103) .... f(200)

= 99(1) for hundreds places + 10(1+2+3+4+5+6+7+8+9) for tens places + 10(1+2+3+4+5+6+7+8+9) for units places + 2 (for 200)

= 99 + 20(45) + 2
= 101 + 900
= 1001

________________________________________________________