Jawabanmu

2014-05-15T18:32:53+07:00
R= 10 cm-> f= 5cm
1/So + 1/Si= 1/f
1/So + 1/20 = 1/5
1/So = 1/5-1/20
1/So= 4/20-1/20
1/So = 3/20
So= 20/3 cm

jadi perbesarannya 
M= Si/So
=20/20/3 = 20x3/20= 3x