Grades 5-6 Video Solutions 2023-2023_1-2

Video Transcription

Question 2. Matchsticks can be used to build numbers as shown. For example, to build the number 15, one needs 7 matchsticks,  and one needs the same number of matchsticks to build the number 8. What is the largest positive number that can be built with 7 matchsticks?  Let's start off from the end, going at our highest possible number, 800. Where to try to build 800 out of matchsticks, we see that this uses too many matchsticks.  Since we cannot build this out of 7 matchsticks, 8 cannot be the answer. Next, we will try our next biggest number, 711.  When we build this out of matchsticks, we realize that this is exactly 7 matchsticks.  So this is the biggest number that we can create out of the ones given, so the answer will be D.

Video Summary

The problem involves determining the largest number that can be built using 7 matchsticks according to a specific configuration. Starting from the largest possible number, 800, and moving downwards, the video concludes that constructing 800 requires more than 7 matchsticks. Subsequently, the number 711 is considered, which can be constructed using exactly 7 matchsticks. Therefore, 711 is identified as the largest number that can be made with 7 matchsticks, making it the correct answer.