Question

From a rectangular cardboard sheet 145 cm long and 32 cm broad, 42 circular plates each of diamater 8 cm have been cut out. Find the area of the remaining portion of the sheet.

Answer 1

Area of rectangular cardboard=l×b
$\: \: \: \: \: \: \: \: = 145 \times 32 \\ \: \: \: \: \: \: \: \: = 4640 {cm}^{2}$
radius =4cm
Area of 42 circular plate=42×(πr^2)
$\: \: \: \: \: \: \: = 42 \times \frac{22}{7} \times 16 \\ \: \: \: \: \: \: \: = 6 \times 22 \times 16 \\ \: \: \: \: \: \: \: = 2112 {cm}^{2}$
Area of remaining portion =area of rectangular cardboard -area of 42 circular plates
=4640-2112

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 2528 {cm}^{2}$
I hope it helps you.