Question 1165289
<pre>
              RATE in TANK per MINUTES

one pipe        4/t

other pipe      1/t

combined        1/63
</pre>

{{{4/t+1/t=1/63}}}

{{{5/t=1/63}}}

{{{t/5=63}}}

{{{t=5*63}}}

{{{t=315}}}  {{{and}}}  {{{(4/315)x=1}}} will give x, the time for the "one" pipe alone to fill the tanker.