:
Explanation:
a varies directly with b
a ∞ b
a = Kb
K is the constant of proportionality
If a = 4 when b = 21
4 = 21×k
4 = 21k
k = 4/21
: - a = 4b/21
find a when b= 7.
a = 4(7)/21
a = 4/3
a = 1 1/3
A(promotional sign)b
A=kb
4=21k
K=0. 1904
A=0. 2b
A=0. 2×7
A=1. 4
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