WAEC - Mathematics (2002 - No. 15)
If (x + 3) varies directly as y and x = 3 when y = 12, what is the value of x when y = 8?
1
\(\frac{1}{2}\)
\(-\frac{}{}\)
-1
Forklaring
\((x+3) \propto y\\
∴x + 3 = ky\hspace{1mm}when\hspace{1mm}x = 3, y = 12\\
3+3 = 12k\\
∴ k = \frac{1}{2}\\
\Longrightarrow x + 3 = \frac{1}{2}y\) to find x when y = 8
\(x + 3 = \frac{1}{2}\times 8\\
x=4-3\\
x = 1\)
∴x + 3 = ky\hspace{1mm}when\hspace{1mm}x = 3, y = 12\\
3+3 = 12k\\
∴ k = \frac{1}{2}\\
\Longrightarrow x + 3 = \frac{1}{2}y\) to find x when y = 8
\(x + 3 = \frac{1}{2}\times 8\\
x=4-3\\
x = 1\)