${Từ}$ ${trang}$ ${3}$ ${đến}$ ${trang}$ ${9}$ ${có}$ ${tất}$ ${cả}$ ${chữ}$ ${số}$ ${là}$ ${:}$
${(}$ ${9}$ ${-}$ ${3}$ ${)}$ ${:}$ ${+}$ ${1}$ ${=}$ ${7}$ ${chữ}$ ${số}$ ${)}$
${Từ}$ ${trang}$ ${10}$ ${đến}$ ${trang}$ ${99}$ ${có}$ ${tất}$ ${cả}$ ${chữ}$ ${số}$ ${là}$ ${:}$
${(}$ ${99}$ ${)}$ ${:}$ ${1}$ ${1}$ ${=}$ ${90}$ ${chữ}$ ${số}$ ${)}$
${Từ}$ ${trang}$ ${100}$ ${đến}$ ${trang}$ ${240}$ ${có}$ ${tất}$ ${cả}$ ${chữ}$ ${số}$ ${là}$ ${:}$
${(}$ ${240}$ ${-}$ ${100}$ ${)}$ ${:}$ ${1}$ ${+}$ ${1}$ ${=}$ ${141}$ ${(}$ ${chữ}$ ${số}$ ${)}$
${Số}$ ${chữ}$ ${để}$ ${đánh}$ ${số}$ ${trang}$ ${là}$ ${:}$
${7}$ ${.}$ ${1}$ ${+}$ ${90}$ ${.}$ ${2}$ ${+}$ ${141}$ ${.}$ ${3}$ ${=}$ ${610}$ ${(}$ ${chữ}$ ${số}$ ${)}$
${Đáp}$ ${số}$ ${:}$ ${610}$ ${chữ}$ ${số}$
