例１.甲、乙、丙、丁与小强五位同学一起比赛象棋，每两人都要赛一盘。到现在为止，甲已经赛了四盘，乙赛了三盘，丙赛了两盘，丁赛了一盘。

问：小强赛了几盘？

推荐阅读：
How to Make Your “Contact Us” Page Kick Ass　 The A to Z of Content Marketing: Habits Every Content Marketer S　 Keeping the Flame Going: How to Rock a Steady Job and Still Have　 How to Use Social Media and User-Generated Content to Boost Traf　 7 Types of Blog Posts and When to Use Them　 How to Maximize Profit From Your Blog Visitors　 Win a Premium WordPress Theme For Your Blog　 Easy Tips for Bloggers to Make Insta-Dough on Instagram　 “Celebrating” World Backup Day 2016　 How the Right Visual Can Transform Any Landing Page