Rates of reaction of zero, first & second order reactions having same magnitude of rate constants are ${\mathrm{\gamma }}_1,{\mathrm{\gamma }}_2,{\mathrm{\gamma }}_3$ respectively. The order of ${\mathrm{\gamma }}_1,{\mathrm{\gamma }}_2,{\mathrm{\gamma }}_3$if the concentration of reactant is lesser than unity.

${\mathrm{r}}_1={\mathrm{k}}_1{\left[\mathrm{A}\right]}^0$;${\mathrm{r}}_2={\mathrm{k}}_2{\left[\mathrm{A}\right]}^1$;${\mathrm{r}}_3={\mathrm{k}}_3{\left[\mathrm{A}\right]}^2$

since concentration [A] < 1

${\mathrm{r}}_1 > {\mathrm{r}}_2 > {\mathrm{r}}_3$

let concentration [A] = 0.1 in each case

${\mathrm{r}}_1={\mathrm{k}}_1{[0.1]}^0$;${\mathrm{r}}_2={\mathrm{k}}_2{[0.1]}^1$;${\mathrm{r}}_3={\mathrm{k}}_3{[0.1]}^2$

${\mathrm{r}}_1={\mathrm{k}}_1$;${\mathrm{r}}_2=\frac{{\mathrm{k}}_2}{10}$;${\mathrm{r}}_3=\frac{{\mathrm{k}}_3}{100}$

since magnitude is same 

${\mathrm{r}}_1:{\mathrm{r}}_2:{\mathrm{r}}_3={\mathrm{k}}_1:\frac{{\mathrm{k}}_1}{10}:\frac{{\mathrm{k}}_1}{100}$

${\mathrm{r}}_1 > {\mathrm{r}}_2 > {\mathrm{r}}_3$