Density is related to Ice. Ice is related to White. White is related to Cake. 
Machine can be used for Calculate. Machine is related to Camera. Camera is related to Picture. Picture is a synonym of Depict. 
Density <--RelatedTo--> Ice <--RelatedTo--> White <--RelatedTo--> Cake 
Calculate <--UsedFor-- Machine <--RelatedTo--> Camera <--RelatedTo--> Picture <--Synonym--> Depict 