Answer 6_2_7

1/f = 1/u + 1/v 

1/40 = 1/20 + 1/v

1/v = 0.025 - 0.05 = -0.025

v = - 40 cm 

magnification = v/u = -40/20 = (-)2

Therefore the image is 4.4 cm across

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