Question 761361


Principle 1: Number of walls built is directly proportional to number of builders. (i.e. more builders, more walls built)
Principle 2: Time taken to build walls is inversely proportional to number of builders (i.e. if you have more builders, it will take a lesser time to build the same number of walls)
Principle 3: Number of walls is directly proportional to the time taken. (i.e. if you have more walls to build, it will take longer - if the number of builders is the same) 

given that:
{{{A}}} can make a wall in {{{10}}} days 
{{{A}}} can make {{{1/10}}} of a wall in {{{1}}} day
 
{{{B}}} can make in {{{20}}} days
 {{{ B}}} can make {{{1/20}}} of a wall in {{{1}}} day

{{{C}}} can make in {{{30}}} days  
{{{C}}} can make {{{1/30}}} of a wall in {{{1}}} day

all together 

{{{1/10+1/20+1/30 =1/x}}} rate

{{{11/60=1/x}}}

so, solve for {{{x}}}

{{{11/60=1/x}}}

{{{11x=1*60}}}

{{{x=60/11}}}

{{{x=5.5}}} days or {{{x=5}}} days and {{{12}}} hours