Math problem in primary school: the area of parallelogram increases by 20 square centimeters after the length increases by 2 centimeters, and the area increases by 45 square centimeters after the height increases by 3 centimeters. The length of the parallelogram is increased by 2 cm, and the area is increased by 20 cm 2, which is equivalent to the height of the parallelogram multiplied by the increased length of 2 cm, because the long area of the parallelogram = length * height.

The formula is (original parallelogram length +2cm) * height = original area +20cm2.

So: the height of parallelogram =20/2= 10 cm.

Similarly, the base of the original parallelogram is 45 ÷ 3 = 15cm.

The area of the original parallelogram is10×15 =150cm2.