Question

a compound lens is made up of two thin lenses having power +12.5d and -2.5d find focal length and power of comnination

Answer 1

5
$5 \times \frac{5}{5} \times \frac{5}{5}$
Sorry for the mistake
It was not suitable for this question. It's for another

Answer 2

P = P1 + P2
P = 12.5 + (-2.5)
P = 10 Dioptre
and,
1/F = 1/f1 + 1/f2 = 10/125 - 10/25 = 8/25
F = 25/8 = 0.32 meter. ANSWER.
thanks...