Notice that a can is a cylinder, which is basically two circles and one rectangle. Now, the question wants area of this rectangle.
You know the width of the rectangle (or the paper), which is 11cm. How do you find the length then?
Notice that the length of the rectangle is also the circumference of the circles. From here, use C = πd where C is circumference and d is diameter. The d is given, which is 7.5 cm. Depending on the question, π can be 3.14, 22/7 or the actual pi.
multiply π and 7.5cm and you get the circumference. Multiply this to 11cm and you get area of the rectangle.
