Question

The perimeter of a protractor with radius r is ........ ​

Answer 1

If the perimeter of a semi-circular protractor is 108 cm, find the diameter of the protractor (Take π=

7

ANSWER

Let the radius of the protractor be r cm. Then,

Perimeter =108cm.

⇒

2

1

(2πr) + 2r = 108 ..........[∴Perimeterofasemicircle=

2

1

(2πr)]

⇒πr+2r=108⇒

7

22

×r+2r=108⇒36r=108×7⇒r=3×7=21

∴ Diameter of the protractor =2r= (2×21)cm=42cm

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