Question

Tính : 15,5.20,8 - 3,5.9,2 - 15,5.9,2 + 3,5.20,8

Answer 1

\(15,5\cdot20,8-3,5\cdot9,2-15,5\cdot9,2+3,5\cdot20,8\)

\(=15,8\left(20,8-9,2\right)+3,5\left(-9,2+20,8\right)\)

\(=15,5\cdot11,6+3,5\cdot11,6\)

\(=11,6\left(15,5+3,5\right)=11,6\cdot19=220,4\)

Answer 2

Ta có: \(15,5.20,8-3,5.9,2-15,5.9,2+3,5.20,8\)

\(=\left(15,5.20,8+3,5.20,8\right)-\left(3,5.9,2+15,5.9,2\right)\)

\(=20,8\left(15,5+3,5\right)-9,2\left(3,5+15,5\right)\)

\(=395,2-174,8=220,4\)