The square chart of length 60 cm can be divided exactly in 7 parts each of length 8 cm along one side of chart paper and exactly in 12 parts each of length 5 cm along other side of chart paper.
The figure shows that the number of rectangular cards which can be made from the square chart paper is 7 × 12 = 84
Now, area of the square chart paper
= (60 × 60) cm2 = 3600 cm2
Area of one rectangular card = (8 × 5) cm2
= 40 cm2
∴ Area of 84 rectangular cards
= 84 × 40 cm2 = 3360 cm2
∴ Area of remaining chart paper = (3600 – 3360) cm2 = 240 cm2