Janelle,
According to my dictionary one acre is 43560 square feet. Thus
1 acre = 43560 sq ft = 43560 12 12 sq inches
But one inch is 2.54 centimeters and there are 100 centimeters in a meter so
1 acre = 43560 12 12 2.54 2.54 sq cm
= 43560 12 12 2.54 2.54 ^{1}/_{100} ^{1}/_{100} = 4046.86 sq meters
Thus 40 acres is 40 4046.86 = 161874.26 square meters.
Penny
