Answer:number of children negative for chicken pox=28
Step-by-step explanation:
Number of children positive for chicken pox =18 out of 30
Therefore number of children negative for chicken pox is 12 out of 30 ie ( 30-18)
Such that the ratio of positive tested chicken pox children to negative tested chicken pox children =18:12
Therefore total ratio =18 +12=30
Suppose there are 70 children,then number of children negative for chicken pox =
12/30 x 70 =28
