<PRE><B>Question 667189</B>
A,B and C can do a piece of work together in 15 days.
B alone can do it in 30 days and C alone can do it in 40 days.
In how many days A alone will do the work?
:
Let a = no. of days required by A alone
let the completed job = 1
:
A typical shared work equation
:
{{{15/a}}} + {{{15/30}}} + {{{15/40}}} = 1
Reduce the fractions
{{{15/a}}} + {{{1/2}}} + {{{3/8}}} = 1
multiply by 8a, results
8(15) + 4a + 3a = 8a
120 + 7a = 8a
120 = 8a - 7a
a = 120 hrs A working alone
:
:
see if that adds up using a calc
{{{15/120}}} + {{{15/30}}} + {{{15/40}}} =
.125 + .50 + .375 = 1; confirms our solution</PRE>