作业帮GRE PP2数学一题提问~题目是这样的： A rectangular game board is composed of identical squares arranged in a rectangular array of r row and r+1 columns. The r rows are numbered from 1 through r, and the r+1 comlumns are numbered from 1 thr
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GRE PP2数学一题提问~题目是这样的： A rectangular game board is composed of identical squares arranged in a rectangular array of r row and r+1 columns. The r rows are numbered from 1 through r, and the r+1 comlumns are numbered from 1 thr
GRE PP2数学一题提问~
题目是这样的： A rectangular game board is composed of identical squares arranged in a rectangular array of r row and r+1 columns. The r rows are numbered from 1 through r, and the r+1 comlumns 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 nor the 7th column?
原题给的答案选项是r2-r请问这题应该怎么想呢?没太看懂题目意思.请大家帮忙解答~多谢!
GRE PP2数学一题提问~题目是这样的： A rectangular game board is composed of identical squares arranged in a rectangular array of r row and r+1 columns. The r rows are numbered from 1 through r, and the r+1 comlumns are numbered from 1 thr
本题选a!
就是r*(r+1)格中去掉第4行第7列的格子后还有几格,
所以
共有:r*(r+1)-(r+r+1)+1
=r^2+r-2r-1+1=r^2-r.
一块长方形板子由同样大小的正方形组成，横着有r 行（标记为第1行，第2行......第 r 行），竖着有 r+1 列（标记为第1列，第2列.....第r+1列）。如果r>10，那么既不在第4列也不在第7列的部分共有多少个正方形？
【其实就是求去掉两列之后的面积】
整个这块长方体的面积是 r*(r+1)，这两列的面积都是r*1
所以去掉这两列之后的面积是 r*(r+1) - ...
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一块长方形板子由同样大小的正方形组成，横着有r 行（标记为第1行，第2行......第 r 行），竖着有 r+1 列（标记为第1列，第2列.....第r+1列）。如果r>10，那么既不在第4列也不在第7列的部分共有多少个正方形？
【其实就是求去掉两列之后的面积】
整个这块长方体的面积是 r*(r+1)，这两列的面积都是r*1
所以去掉这两列之后的面积是 r*(r+1) - r - r =r^2 - r
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