What will be the cost of gardening 1 m broad boundary around a rectangular plot having a perimeter of 340 m at the rate of Rs.10 per square metre?

Take an inner rectangle ABCD to be the plot . Let its sides be x,y .

After taking 1 m margin the sides of the new and bigger rectangle PQRS become ( x+2 ) , ( y+2 ) .

We have 2(x+y) = 340 ..... [1]

Now to get the area of the margin subtract area of ABCD from PQRS ...

( x+2 ) ( y+2 ) - xy
xy + 2x + 2y + 4 - xy
2x + 2y + 4
2 ( x + y ) + 4
340 + 4
344

Now this is the area of that band In sq m ...

Multiplying it by cost for 1 sq m ...

344 x 10
3440.

B is correct choice.