请教一道数学题

FutureChaoUID: 2859515

在模考的时候碰到一道数学题没有想明白，请各位指点：

A rectangular game board is composed of identical squares arranged in a rectangular array of r rows and r+1 columns. The r rows are numbered form 1 through r, and the r+1 columns numbered from 1 through r+1. If r>10, which of the following represent the number of squares on the board that are neither in the 4th row nor in the 7th column?
r^2-r

r^2-1

r^2

r^2+1

r^2+r


想了半天没有想出来，感觉要载在ETS的数学上了，求各位gter帮帮忙～～多谢！

sagisoloUID: 2720349

r行，r+1列中去掉一行一列变成r-1行，r列

所以总共有r(r-1)个方格选A吗？

hua11UID: 3027785

楼上正解啊，就是说本来r（r+1）个格子去掉第4行的格子和第7列的格子，剩下多少个呢？
r（r－1）个

FutureChaoUID: 2859515

原来是这个意思，我没有看明白题目，谢谢两位！

答案确实是A