The length of a rectangle is increased by 60%. By what percent would the width have to be decreased to maintain the same area?

37.50%

Let us assume the length to be 10 and breadth as 10. So, the area i.e. l x b = 100

After increase in length i.e. 16

Area = l x b 

100 = 16 x b

b = 6.25

Difference = 3.75

Difference in percentage = \(\frac{3.75 }{10 }\) x 100 = 37.5%