tolong dikerjakan. bsk dikumpul pake cara!

diketahui:
fob : 2 mm
fok : 50 mm
sob : 2.2 mm

ditanya: d

jawab:

1/fob = 1/sob + 1/s'ob
1/2 = 1/2.2 + 1/s'ob
1/s'ob = 0.5 - 0.45 = 0.05
s'ob = 1/0.05 = 20 mm

d = s'ob + (250 x fok)/(250 + fok)
d = 20 + (250 x 50)/(250 + 50)
d = 20 + 12500/300
d = 20 + 41.67
d = 61.67 mm