Janet designed a star on her computer and each side had a length of 40 mm. She reduced the figure by a scale factor of 0.65. Whi
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Answer:
Option (B) is correct .
The constant of proportionality is 7.5 .
Reason
Let us assume that the number of books be x.
Let us assume that the cost of books be y .
Than
y = kx
Where k is constant of proportionality .
As given
Number of Books 4 6 8
Cost ($) 30 45 60
Thus
when x = 4 , y = 30
Put in the equation y = kx .
k = 7.5
when x = 6 , y = 45
Put in the equation y = kx .
k = 7.5
when x = 8 , y = 60
Put in the equation y = kx .
k = 7.5
Therefore the constant of proportionality is 7.5 i.e option (B) is correct .