What percentage change is made in the area of a rectangle by decreasing its length and increasing its breadth by 15% and 20% respectively?

Text Solution

20% increase20% decreaseNo change 4% decrease

Answer : D

Solution : Let the length be l and breadth be b m. <br> then , original area `=(lxxb) m^(2)= lb m^(2)`. <br> `"New length "=(lxx(120)/(100))m=(6l)/(5) ,"new breadth "=(bxx(80)/(100))m=(4b)/(5)m.` <br> `"New area "=((24lb)/(25))m^(2)=96m^(2)."change in area" =(ab-(24lb)/(25))m^(2)=(lb)/(25)m^(2).` <br> `therefore % " Change " =(lbxx100)/(25xxlb)%= 4%.`

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