A6. If we increase one edge of a cuboid by $10 \%$, the second by $20 \%$, and the third by $25 \%$, by what percentage will the volume of the cuboid increase?
(A) $60 \%$
(B) $65 \%$
(C) $69 \%$
(D) $72 \%$
(E) $90 \%$

## 6th National Mathematics Knowledge Competition for Vocational School Students

## April 22, 2006

## Part II: LONGER PROBLEMS

Instruction: Solve problems B1 to B4 of the second part on the provided paper, where you write down the complete calculations. Read each problem carefully and answer the questions asked. The solution to each of these problems will be scored from 0 to 7 points.

Note that you have 90 minutes to solve the problems in both parts.
A6. The volume $V=a b c$ represents $100 \%$. If we extend one edge by $10 \%$, the second by $20 \%$, and the third by $25 \%$, the volume $V^{\prime}=1.1 a \cdot 1.2 b \cdot 1.25 c=1.65 V$ or $165 \%$ of the original volume. The volume increases by $65 \%$.

II. PART