Question 694284
{{{x}}}= amount carried before entering door #1 (in Rs)
after paying Rs. 25 fee to enter, you have {{{x-25}}}.
At this point you are inside the parlour, so your money doubles to
{{{2(x-25)}}}.
You pay Rs. 25 to come out thru door no. 2, and again Rs. 25 to get inside thru door no. 3, ending up with
{{{2(x-25)-25-25}}}.
At this point you are inside the parlour, so your money doubles to
{{{2(2(x-25)-25-25)}}}.
Then you pay Rs. 25 to come out thru door no. 4 with
Rs. {{{2(2(x-25)-25-25)-25}}}.
Since you came out with no money left,
{{{2(2(x-25)-25-25)-25=0}}}.
Simplifying:
{{{2(2(x-25)-25-25)-25=0}}} --> {{{2(2(x-25)-50)-25=0}}} --> {{{2(2x-50-50)-25=0}}} --> {{{2(2x-100)-25=0}}} --> {{{4x-200-25=0}}} --> {{{4x-225=0}}}
Solving:
{{{4x-225=0}}} --> {{{4x-225+225=0+225}}} --> {{{4x=225}}} --> {{{4x/4=225/4}}} --> {{{highlight(x=56.25)}}}