Q1 of 18 Page 213

For each pair of quantities given below, check whether the first is proportional to the second. For proportional quantities, calculate the constant of proportionality.

Perimeter and radius of circles.

Perimeter and radius of circle.


Let the perimeter be y and radius of circle be r.


Perimeter = 2πr


⇒ y = 2 × π × r


⇒ y = 2πr


We can whatever value we like for x on right side of the above equation. So, x is a variable.


Whatever value we give for r, that the value will be multiplied by a constant 2π. So, y will always be proportional to nr.


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For each pair of quantities given below, check whether the first is proportional to the second. For proportional quantities, calculate the constant of proportionality.

Area and radius of circles.

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For each pair of quantities given below, check whether the first is proportional to the second. For proportional quantities, calculate the constant of proportionality.

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