Which least number should be subtracted from 1000 so that the difference is exactly divisible by 35?

To find the least number to be subtracted from 1000 so that the difference is exactly divisible by 35, we divide 1000 by 35 and find the remainder.

$\begin{array}{l} \phantom{x^2 }{\quad 28} \ 35\overline{\smash{\big)}1000} \ \phantom{x}\phantom{()}\underline{-70} \ \phantom{{x^2 }+} 300 \ \phantom{{x}()}\underline{-280} \ \phantom{{x^2 +(}} 20 \ \end{array}$

The remainder when 1000 is divided by 35 is 20.

So, the least number to be subtracted from 1000 = 20.

Therefore, 1000 - 20 = 980, which is exactly divisible by 35.

Hence, the least number to be subtracted from 1000 is 20.