"A certain number of person can dig a trench 100 m  long , 50 m broad and 10 m
Channel: Doubtnut
Date: 2020-04-12

"A certain number of person can dig a trench 100 m
  long , 50 m broad and 10 m deep in 10 days. The same number of persons can
  dig another trench 20 m broad and 15 m deep in 30 days. The length of the
  second trench is
`400\ m`
b. `800\ m`
c. `500\ m`
d. `900\ m`"