Three builder friends Elly, Glen, and Mistri work in the same construction company. Glen can build a wall in the same time as Elly and Mistri will build working together. If Glen and Mistri can make the wall in 8 days while Elly makes it in 40 days alone then how much time will it take Mistri to make the same wall on his own?

answer is

Step-by-step explanation:

Object distance (u) = -100cm  Focal length (f) = 50cm Image distance = v  By lens formula; 1v−1u=1f1v−1u=1f ⇒ 1v−1−100=1501v−1−100=150 ⇒1v=150−11001v=150−1100 ⇒1v=2−1100−11001v=2−1100−1100 v =100cm  Hence the image is formed at 100 cm behind the lens.  Object distance (u) = -100cm  Focal length (f) = -25cm  Image distance = v  By lens formula;Read more on Sarthaks.com - https://www.sarthaks.com/951256/an-object-is-kept-at-a-distance-of-100-cm-from-each-of-the-above-lenses-calculate-the?show=951265#a951265