|
Question 571098: 8 men can dig 168 ft in 7 hours, 3 men can backfill 120 ft in 4 hours; in how many hours can 5 men can dig and backfill 300 ft.?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! 8 men can dig 168 ft in 7 hours, 3 men can backfill 120 ft in 4 hours; in how many hours can 5 men can dig and backfill 300 ft.?
-----
time is indirectly related to # of men and directly related to dig-distance.
---------------------
t = k*d/n
-----
Solve for "k" using "8 men can dig 168 ft in 7 hrs".
7 = k*168/8
k = (8*7)/168 = 1/3
Dig Equation: t = (1/3)d/n
---------------------------
3 men can backfill 120 ft in 4 hours
time is directly related to fill-distance and indirectly related to # of men.
t = k*d/n
----
Solve for "k":
4 = k*120/3
k = 12/120
k = 1/10
Fill Equation: t = (1/10)d/n
---------------------
Question: in how many hours can 5 men can dig and backfill 300 ft.?
Dig: t = (1/3)300/5 = 20 hrs
Fill: t = (1/10)300/5 = 6 hrs
---
Total time: 26 hrs
=================================
Cheers,
Stan H.
===========================
t
|
|
|
| |
