Question 906378
you got right answer

the book answer is wrong, should be {{{12m}}}

if the length of plot is {{{120m}}} (as book suggests) and length(l)=4*breadth(b), then width will be {{{b=l/4=120m/4=30m}}}

so, the total area of plot would be {{{A=lb=120m*30m=3600m^2}}}
but, you are given that a playground measuring {{{12m^2}}} occupies {{{one }}}{{{third}}} of total area of plot

since total area of plot is {{{A=3600m^2}}}, one third of it will be {{{(1/3)A=3600m^2/3=1200m^2}}}, which is NOT what you are given

try with length {{{l=12m}}}, then width {{{b=3m}}}

 the total area of plot would be {{{A=lb=12m*3m=36m^2}}}

one third of it will be {{{(1/3)A=36m^2/3=12m^2}}}, which IS what you are given