The range of a projectile when launched at angle $\theta$ is same as when launched at angle $2 \theta$. What is the value of $\theta$ ?

Balls $A$ and $B$ are thrown from two points lying on the same horizontal plane separated by a distance $120\,m$. Which of the following statement$(s)$ is/are correct.

Projectiles $A$ and $B$ are thrown at angles of $45^{\circ}$ and $60^{\circ}$ with vertical respectively from top of a $400 \mathrm{~m}$ high tower. If their ranges and times of flight are same, the ratio of their speeds of projection $v_A: v_B$ is :

A ball is projected upwards from the top of tower with a velocity $50\,\,m{s^{ - 1}}$ making an angle ${30^o}$ with the horizontal. The height of tower is $ 70 \,m$. After how many seconds from the instant of throwing will the ball reach the ground  ........ $\sec$

At $t = 0$ a projectile is fired from a point $O$(taken as origin) on the ground with a speed of $50\,\, m/s$ at an angle of $53^o$ with the horizontal. It just passes two points $A \& B$ each at height $75 \,\,m$ above horizontal as shown The distance (in metres) of the particle from origin at $t = 2$ sec.

The range of a particle when launched at an angle of ${15^o}$ with the horizontal is $1.5 \,km$. What is the range of the projectile when launched at an angle of ${45^o}$ to the horizontal ........ $km$