一道PP数学题

yuanleiliangUID: 2866246

题目没看懂，希望大家帮忙解答一下，谢！！！

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 from 1 through r, and the r+1 columns are numbered from 1 through r+1. If r >10, which of the following represents the number of squares on the board that are neither in the 4th row nor in the 7th column?

(A) r·(r-1)
(B) r·r - 1
(C) r·r
(D) r·r + 1
(E) r·(r+1)

二哥95万年UID: 3180011

1# yuanleiliang
board由r行，r+1列的格子组成，既不含第4行又不含第7列，共有多少个格子，r*(r+1)-r-(r+1)+1=r^2-r

yuanleiliangUID: 2866246

谢了哈！