Gating ratio of $$1:2:4$$ is used to design the gating system for magnesium alloy casting. This gating ratio refers to the cross section areas of the various gating elements as given below

$$1.$$ $$Down$$ $$sprue$$ $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ $$2.$$ $$runner$$ $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ $$3.$$ $$Ingates$$
The sequence of the above elements in the ratio $$1:2:4$$ is

A casting of size $$100\,\,mm \times 100\,\,mm \times 50\,\,mm$$ is required. Assume volume shrinkage of casting $$2.6\% $$. If the height of the riser is $$80$$ $$mm$$ and riser volume desired is $$4$$ times the shrinkage in casting, what is the appropriate riser diameter in $$mm?$$

A $$10$$ $$mm$$ thick steel bar is to be horizontally cast with two correctly spaced top risers of adequate feeding capacity. Assuming end effect without chill, what should be the theoretical length of the bar?