Question

An object is kept at a distance of 60cm in front of a convex lens. Its real and inverted image is formed ag a distance of 20cm from the lens.find the focal length of the lens

Answer 1

u=-60

v=20

1/f=1/v-1/u

=1/20+1/60

=3+1 /60

=4/60

f=15 cm

Answer 2

3) Solve by

4) Difference between two numbers is 3, the sum of three times the bigger

number and two times the smaller number is 19. Then find the numbers.