A gun mounted on the ground fires bullets in all directions with same speed. The farthest distance the bullets could reach is 6.4 m. The speed of the bullets from the gun is ______ m/s.

(take $$g = 10$$ m/s$$^2$$)

For a projectile fired with initial speed $$u$$ at an angle $$\theta$$ to the horizontal, the horizontal range is given by
$$R = \frac{u^{2}\sin 2\theta}{g}$$.

The range becomes maximum when $$\sin 2\theta = 1$$, i.e. when $$2\theta = 90^{\circ}$$ or $$\theta = 45^{\circ}$$. Hence the maximum range is
$$R_{\max} = \frac{u^{2}}{g}\,\,\,\,\,\,\,-(1)$$

Given $$R_{\max} = 6.4\text{ m}$$ and $$g = 10\text{ m/s}^{2}$$. Substituting these values in $$(1)$$:
$$6.4 = \frac{u^{2}}{10}$$

$$u^{2} = 6.4 \times 10 = 64$$

$$u = \sqrt{64} = 8 \text{ m/s}$$

Therefore, the speed of the bullets is 8 m/s.