Question

what is the least 4-digit number that is exactly divisible by 21?

Answer 1

Dear student

$$\begin{gathered} \mathrm{least}\mathrm{four}\mathrm{digit}\mathrm{number}=1000 \\ \mathrm{On}\mathrm{dividing}1000\mathrm{by}21\mathrm{we}\mathrm{get}\mathrm{remainder}\mathrm{as}13\mathrm{and}\mathrm{quotient}\mathrm{as}47. \\ \mathrm{Now},\mathrm{subtract}\mathrm{remainder}13\mathrm{from}21\mathrm{and}\mathrm{we}\mathrm{get}8. \\ \mathrm{Now},\mathrm{add}8\mathrm{to}1000\mathrm{to}\mathrm{get}1008. \\ \mathrm{Therefore},1008\mathrm{is}\mathrm{the}\mathrm{least}\mathrm{four}\mathrm{digit}\mathrm{number}\mathrm{which}\mathrm{is}\mathrm{exactly}\mathrm{divisible}\mathrm{by}21. \end{gathered}$$
Regards