The actual area of a rectangle is 60 Cm², but while measuring its length a student decreases it by 20% and the breadth increases by 25%. The percentage error in area, calculated by the student is :

Explanation:-

100 ---- 25% ↑ ---> 125 ----- 20% ↓ -----> 100.
So there is no change in the area of rectangle.

Alternatively :

Let area be 1.
Area of rectangle,
= l *b
= 0.8 *1.25
= 1.