18 hemispheres of the same size are made from melting a solid cylinder of 36 cm diameter and 8 cm height, then the diameter (in centimeters) of each hemisphere is \( \left(\right. \) Take \( \left.\pi=\frac{22}{7}\right) \)

Find the equation of line perpendicular to \( 5 x-3 y+4=0 \) that passes through the point \( (-4,1) \).

A ball bounces \( \frac{1}{2} \) of its previous height on each bounce. Find the total distance covered by the ball, until it comes to rest, if it is dropped from a height of 20 metres.

Determine if the following lines are parallel, perpendicular, or neither \[ \begin{array}{l}y=\frac{8 x}{7}-1 \\ -x+3 y=1\end{array} \]

สระน้ำรูปวงกลมมีรัศมียาว 24.5 เมตร ถ้าเดินรอบสระน้ำ 2 รอบ จะได้ระยะทางกี่เมตร \( \left(\pi \approx \frac{22}{7}\right) \)

Angles 3 and 5 are \( \square \) and \( m \angle 5 \) is \( (2 x+11)^{\circ} \).