Grades 9-10 Video Solutions 2025-2025_9-10

Video Transcription

Problem 1. The trifle leaflet shown below includes transparent windows, allowing what is below to be clearly seen when the flaps are folded over. We fold over the left flap  and then the right flap. What is the sum of the numbers that can be seen through the windows?  So here these are the windows, and we're going to fold over first the left flap over this line here, and then this right flap over this line. So the left flap comes first, and so  let's see what happens when we fold over the left flap. So we're going to fold over this line, and we're going to see that this right column of the left flap is going to cover  this left column of the numbers, and the bottom row of the left flap will cover the bottom row of the numbers, so it is going to look like this. Now we need to fold over the right  flap. So we have that the left column of the right flap is now going to cover this right column of the numbers, and the bottom row is going to cover the bottom row, so it's  going to look like this. Now the two numbers that are left that we can still see are 9 and 5, and their sum is 14, so the answer is D.

Video Summary

The problem involves folding a trifold leaflet with transparent windows to identify visible numbers. When the left flap is folded over, it covers specific columns and rows of numbers. Next, folding the right flap also covers additional columns and rows. After both flaps are folded, only numbers 9 and 5 remain visible through the windows. The sum of these visible numbers is 14. Therefore, the solution to the problem is the sum of these numbers, which equals 14.

Keywords

trifold leaflet

transparent windows

visible numbers

folding flaps

sum of numbers