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, 2007

Combinatorics Difficulty 3.0 AMC 10/12 Find the answer Canada

The whole numbers from 1 to 1000 are written. How many of these numbers have at least two 7's appearing side-by-side?

(A) $10$ (B) $11$ (C) $21$ (D) $30$ (E) $19$

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project. Solutions are the publisher's, linked not copied.