At a math conference, the following exchange rates are used:

$$
\begin{aligned}
1 \text { calculator } & =100 \text { rulers } \\
10 \text { rulers } & =30 \text { compasses } \\
25 \text { compasses } & =50 \text { protractors }
\end{aligned}
$$

How many protractors are equivalent to 1 calculator?
(A) 400
(B) 600
(C) 300
(D) 500
(E) 200
From the first exchange rate, 1 calculator is worth 100 rulers.

From the second exchange rate, 100 rulers are worth $\frac{100}{10}(30)=300$ compasses.

From the third exchange rate, 300 compasses are worth $\frac{300}{25}(50)=600$ protractors.

From this, we can see that 600 protractors are equivalent to 1 calculator.

ANSWER: (B)