---
title: The dog that runs back and forth — a lesson of Mova's school · trees and pragmatics
description: «The dog that runs back and forth», a lesson of the lessons course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Do not follow each trip of the dog: only ask how long it runs.
---

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# The dog that runs back and forth

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Lesson 170 of the lessons course of Mova's primary school: 4 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0).

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- [0](https://md.mova.elamur.ai/free/en/corpora/school/lessons/170-the-dog-between-two-walkers/0/) — Do not follow each trip of the dog: only ask how long it runs.
- [1](https://md.mova.elamur.ai/free/en/corpora/school/lessons/170-the-dog-between-two-walkers/1/) — It runs for exactly as long as the two people walk until they meet.
- [2](https://md.mova.elamur.ai/free/en/corpora/school/lessons/170-the-dog-between-two-walkers/2/) — Two people 1200 m apart walk towards each other at 50 and 70 m a minute: they meet after 1200 / (50 + 70) = 10 minutes.
- [3](https://md.mova.elamur.ai/free/en/corpora/school/lessons/170-the-dog-between-two-walkers/3/) — A dog that runs between them at 200 m a minute all that time runs 200 × 10 = 2000 m, however many times it turns.

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