Answer:
perimeter of the rectangle=100cm
or. 2(l+b)=100cm
or. 2(35+b)=100cm
or 70+2b=100cm
or. 2b=100cm-70cm
or. 2b=20xm
or. b=20cm/2
. b=10cm
missing length of rectangle=10cm
Square meters. Centimeters would be too small, meters measure one dimension, and cubic meters measure three dimensions. We need to measure two dimensions, so we use square meters.