The average height of 12 girls out of a class of 20 is 161 cm. and that of the remaining girls is 158 cm. The average height of the whole class is :
Choose one:
A) 142.3 cms
B) 162.3 cms
C) 160.5 cms
D) 142.8 cms
E) 159.8 cms
159.8 cmsxplanation:   Average height of the whole class =(12×161+8×158/20)=159.8 cms   Answer 159.8 cms
<result>E</result>
The average height of 12 girls out of a class of 20 is 161 cm. and that of the remaining girls is 158 cm. The average height of the whole class is :