If the base of a rectangular is increased by 10% and the area is unchanged , then the corresponding altitude must to be decreased by?

Let base = b and altitude = h
Then, Area = b x h
But New base = 110b / 100 = 11b / 10
Let New altitude = H
Then,
Decrese = (h - 10h /11 )
= h / 11
∴ Required decrease per cent
= (h/11) x (1 / h ) x 100 %
= 9¹/₁₁ %