Rate law for $2\mathrm{A}+\mathrm{B}\to \mathrm{C}+\mathrm{D}$ from following data : 
 

S.No	[A] (M)	[B] (M)	Rate (M/s)
1	0.01	0.01	2.5
2	0.01	0.02	5
3	0.03	0.02	45

From the given data, Let Initial rate=2.5

If [B]=doubled $\Rightarrow$Rate= doubled=2(2.5)=5

If [A]=tripled $\Rightarrow$Rate becomes 3² times =3²(2.5)

$\therefore \mathrm{Rate} \mathrm{law}=\mathrm{K}{\left[\mathrm{A}\right]}^2\left[\mathrm{B}\right]$