Answer:
840 cm
Explanation:
From the diagram attached, the 3 by 3 grid is made up of nine 1 cm x 1 cm squares. The the length of wire needed to make this grid consist of four rows each row having a length of 3 cm and four columns with each column having a length of 3 cm.
The length of wire required by the 3 by 3 grid = 4 column (3 cm / column) + 4 row (3 cm / row) = 12 cm + 12 cm = 24 cm
The 20 by 20 grid is made up of twenty 1 cm x 1 cm squares. The the length of wire needed to make this grid consist of twenty one rows each row having a length of 20 cm and twenty columns with each column having a length of 20 cm.
The length of wire required by the 20 by 20 grid = 21 column (20 cm / column) + 21 row (20 cm / row) = 420 cm + 420 cm = 840 cm