Question 33

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waecmaths question: 

G varies directly as the square of H. If G is 4 when H is 3, find H when G = 100

Option A: 

15

Option B: 

25

Option C: 

75

Option D: 

225

waecmaths solution: 

$\begin{align}  & G\propto {{H}^{2}} \\ & G=k{{H}^{2}}\text{  }\!\!\{\!\!\text{ }k=constant proportionality\text{ }\!\!\}\!\!\text{ } \\ & 4=k({{3}^{2}}) \\ & k=\frac{4}{9} \\ & \text{When }G=100 \\ & 100=\frac{4}{9}{{H}^{2}} \\ & {{H}^{2}}=\frac{900}{4} \\ & H=\sqrt{\frac{900}{4}}=\frac{30}{2}=15 \\\end{align}$

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