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Asked by  | 22nd Mar, 2013, 12:07: PM

Expert Answer:

u+v = 70
v = 70-u
hi/ho = v/u
40/100 = 70-u / u
4/10 = 70-u / u
14u = 700
u = 50 cm
v = 70-50 = 20 cm
1/v - 1/u = 1/f
1/20 - 1/50 = 1/f
5-2/100 = 1/f
f = 100/3 = 33.3 cm

Answered by  | 22nd Mar, 2013, 06:05: PM

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