Question

tính bằng cách hợp lí

4,2*12,5+0,6*9,25*7-2,1*1,75*2

Answer 1

\(=4,2\cdot12,5+4,2\cdot9,25-4,2\cdot1,75\)

\(=4,25\left(12,5+9,25-1,75\right)=4,25\cdot20=85\)

Answer 2

\(4,2\times12,5+0,6\times9,25\times7-2,1\times1,75\times2\)

\(=4,2\times12,5+\left(0,6\times7\right)\times9,25-\left(2,1\times2\right)\times1,75\)

\(\text{= 4,2 x 12,5 + 4,2 x 9,25 – 4,2 x 1,75}\)

\(\text{= 4,2 x (12,5 + 9,25 – 1,75)}\)

\(\text{= 4,2 x 20}\)

\(\text{= 84}\)