Question

the radius of a circular cardboard is 20 CM a strip of width a strip of 4 cm is removed all the along its border the percentage of the area of the strap removed is

Answer 1

Find area of the circle:

Area = πr²

Area = π(20)² = 400π cm²

Find the area of the circle without the strip:

Radius = 20 - 4 = 16 cm

Area = πr²

Area = π(16)² = 256π cm²

Find the area of the strip:

Area = 400π - 256π  = 144π cm²

Find the percentage of the strip:

Percentage = 144π/400π x 100 = 36%

Answer: The strip is 36% of the cardboard

Answer 2

First find the area of the strip removed with radius 20cm the area will be ....πr² =22/7 × 400=1257.1cm

Radiuse (20cm-4cm) = 16cm

Area of the 16cm radius using πr² = 804.57cm

The difference of 1257.1 -804.57 = 452.53cm

Therefore the percentage removed 452.53/1257.1×100= 35.99% ~ 36% ans