nifica Calculează grupând favorabil factorii 2x 3 x 4 x 5 = 10 X 7 X 3 X 10 - 20x7x3

2x3x4x5=2x5x3x4=10x12=120
10x7x3x10=10x10x7x3=100x21=2100
20x7x4=140x4=560