Topic: Max and Min

Today we talked about problems that ask you to find the maximum or minimum value in the given situation. Depending on the type of problems (e.g. number problems, shape problems, etc), the strategies can be different.  However, one common strategy is to find a valid answer first (usually the most obvious one), and try to improve it: find a smaller answer if the question asks for "least" possible value; and vice versa.

Homework

1. Two three-digit numbers have all their six digits distinct. The first digit of the second number is twice the last digit of the first number. What is the smallest possible sum of two such numbers?

A. 552 B. 546 C. 301 D. 535 E. 537

2. In some of the small squares of a 2x9 grid there are coins. Each small square either contains a coin or has a common side with a similar square containing a coin. The number of coins in the grid must then be at least:

A. 5 B. 6 C. 7 D. 8 E. 9