The radius of a wheel is $3.5 \, cm$. What is the distance (in $cm$) travelled by the wheel in $20$ revolutions?

$A$ plane divides a right circular cone into two parts of equal volume. If the plane is parallel to the base,then the ratio,in which the height of the cone is divided,is

Water is flowing at the rate of $3 \, km/h$ through a circular pipe of $20 \, cm$ internal diameter into a circular cistern of diameter $10 \, m$ and depth $2 \, m$. In how much time will the cistern be filled?

If a sphere of radius $r$ is divided into $4$ identical parts,then the total surface area of the $4$ parts is

Marbles of diameter $1.4\, cm$ are dropped into a cylindrical beaker containing some water and are fully submerged. The diameter of the beaker is $7\, cm.$ Find how many marbles have been dropped in it if the water rises by $5.6\, cm.$

$A$ cube of edge $3\, cm$ of iron weighs $12\, gm$. What is the weight of a similar cube of iron whose edge is $12\, cm$? (in $gm$)