A10. If you open a book and add the numbers that mark the left and right page, you get 21. What number do you get if you multiply the same two numbers?
(A) 100
(B) 121
(C) 420
(D) 110
(E) 200

# 4th Regional Mathematics Knowledge Competition for Vocational School Students

March 31, 2004

## II. Part: 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 rated from 0 to 5 points.

Note that you have 90 minutes to solve the problems of the first and second parts.
A10. The left and right pages of a book are marked with consecutive numbers, so $21=10+11$, and the product is $10 \cdot 11=110$.

## II. PART