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The second semester of grade seven. Vertical lines and diagonal lines. Math exercises. Urgently beg. .
0 straight lines 1 block = 1

1 straight line and 2 blocks = 1+ 1

Two straight lines and four blocks = 1+ 1+2.

Three straight lines and seven blocks = 1+ 1+2+3.

Four straight lines 1 1 block = 1+ 1+2+3+4.

Six straight lines 1+ 1+2+3+4+5+6=22 blocks.

N straight lines can be divided into1+1+2+...+n = (1+n) n/2+1.