Simple calculation of 0.25 * 5.2 * 1.9

Simple calculation of 0.25 * 5.2 * 1.9

5.2/4=1.3
0.25*4=1
The original formula is 1.3 * 1.9
One is direct calculation, the other is square difference formula
1.6*1.6-0.3*0.3