A box contains 14 disks, each coloured red, blue or green. There are twice as many red disks as green disks, and half as many blue as green. How many disks are green?
(A) 2
(B) 4
(C) 6
(D) 8
(E) 10
Solution 1

Since there are twice as many red disks as green disks and twice as many green disks as blue disks, then there are four times as many red disks as blue disks.

So the total number of disks is seven times the number of blue disks (since the numbers of red and green disks are four and two times the number of blue disks).

Since there are 14 disks in total, there are 2 blue disks, and so there are 4 green disks.

## Solution 2

Let the number of green disks be $g$.

Then the number of red disks is $2 g$, and the number of blue disks is $\frac{1}{2} g$.

From the information given,

$$
\begin{aligned}
2 g+g+\frac{1}{2} g & =14 \\
\frac{4}{2} g+\frac{2}{2} g+\frac{1}{2} g & =14 \\
\frac{7}{2} g & =14 \\
g & =\frac{2}{7} \times 14 \\
g & =4
\end{aligned}
$$

Therefore, the number of green disks is 4 .

ANswer: (B)