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.

Area and radius of circles.

Area and radius of circle


Let the area be y and radius be r


Area = πr2


⇒ y = π × r2


⇒ y = πx2


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


Whatever value we give for r, that the value will be multiplied by a constant π and the variable r. That means r is not multiplied by the same constant every time.


So, y is not proportional to r.


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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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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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