Question 12

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Jambmaths question: 

x varies directly as the product of u and v and inversely as their sum. If x =3 when u = 3 and v =1. What is the value of x if u = 3 and v =3

Option A: 

3

Option B: 

4

Option C: 

6

Option D: 

9

Jamb Maths Solution: 

$\begin{align}  & x\propto \frac{uv}{u+v} \\ & x=\frac{kuv}{u+v} \\ & \text{When }u=3,v=1,x=1 \\ & 3=\frac{k(3)(1)}{3+1} \\ & 3=\frac{3k}{4} \\ & k=4 \\ & \text{When }u=3,\text{ }v=3 \\ & x=\frac{4\times 3\times 3}{3+3}=\frac{36}{6}=6 \\\end{align}$

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