a<-c(10, 2, 19, 24, 6, 23, 47, 24, 54, 77)
n<-length(a) # now n is equal to the number of elements in a

mean(a)
1/mean(1/a) # compute the harmonic mean
prod(a)^(1/n) # compute the geometric mean

b<-c(30,60)
mean(b)
1/mean(1/b)

c<-c(120,130,118)
m<-length(c)
round(mean(c),digits=2)
round(prod(c)^(1/m),digits=2)

g<-((9204/5000)^(1/3)-1)*100
round(g, digits=2)