If the room is a rectangle, use a meter stick to measure the two unequal sides of the room. For example, one side is 5 meters, the other side is 7 meters. Then the Area is 5*7=35 m^2 (35 square meters).

(If the sides are equal, so the room is a square, such as 5 m and 5 m, then 5*5=25 square meters).

----5----

| ..........|

|7.........|

| ..........|

| ..........|

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If the room isn't a rectangle, say it has a corner in it, then split the room into two rectangles, and add the results together. For example, if the 2nd rectangle was 2 m on one side and 3 m on the other, then 2*3=6 square meters, plus the 35 that we had before, which = 41 square meters.