Floor Function Sum?

Let $\left\lfloor x \right\rfloor$ denote the greatest integer less than or equal to $x$ . Find the value of $\left\lfloor \frac { 2 }{ 5 } \right\rfloor +\left\lfloor \frac { 4 }{ 5 } \right\rfloor +\left\lfloor \frac { 6 }{ 5 } \right\rfloor +...+\left\lfloor \frac { 48 }{ 5 } \right\rfloor$ .

Do not use a calculator and try to do it under 5 minutes.