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Let the initial length be l.
and the rate per metre be r.
if l+5, then r-2
cost remain unchanged, however.
Initial cost: l*r
Modified cost: (l+5)*(r-2)
As cost remain unchanged,
l*r=(l+5)*(r-2) = 200
l*r=l*r+5*r-2*l-10
5r-2l=210
Also r=200/l
5*(200/l)-2l=210
1000/l-2l=210
1000-2*l^2=210*l
2*(l^2)-210*l-1000=0
By solving this quadratic equation, we get
l=4.563561052566634 m
r=43.82542442102669 Rs/m
Second answer of this quadratic equation gives negative length, hence discarded.
and the rate per metre be r.
if l+5, then r-2
cost remain unchanged, however.
Initial cost: l*r
Modified cost: (l+5)*(r-2)
As cost remain unchanged,
l*r=(l+5)*(r-2) = 200
l*r=l*r+5*r-2*l-10
5r-2l=210
Also r=200/l
5*(200/l)-2l=210
1000/l-2l=210
1000-2*l^2=210*l
2*(l^2)-210*l-1000=0
By solving this quadratic equation, we get
l=4.563561052566634 m
r=43.82542442102669 Rs/m
Second answer of this quadratic equation gives negative length, hence discarded.
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