Grades 3-4 Video Solutions 2023-2023_3-4

Video Transcription

Problem number 23. Teacher Claire wants to write the numbers 1 to 7 in the circles. Inside each circle, she writes one number. She wants the sum of the numbers in two  neighboring circles to match the number shown on the connecting line. What number must she write inside the green circle?  Here's a close-up of the circle. These sums are rather large. There are a lot of 9s, 8s, 7s, and 6s. The trick to this problem is figuring out where the 1 is going to go.  Because the numbers only go from 1 to 7, the 1 at most can make a sum of 8.  So the 1 cannot go next to any of the connecting lines that have a 9 on them.  So the green circle can't be 1. Also, this circle cannot be 1. And this circle cannot have a 1 in it because there's a 9 on this side.  Also means this circle cannot have a 1 in it.  The circle between the 7 and the 8 is a possibility for the number 1. This circle cannot have the number 1 because there's a 9 here.  And the circle on the other side of 9 also cannot have the 1 in it.  So we found where the number 1 goes. Here on top.  We can use this to figure out where the other numbers are.  Because the number on the segment is a sum of two numbers,  there's going to be only one possibility for the number here.  1 plus 7 gives 8.  If we go this direction, 1 plus 6 gives 7.  Let's continue on this side. 7 plus 2 makes 9.  And 2 plus 4 will make 6.  Let's finish filling in the numbers to make sure that we have the right answer with 4 here in the green circle.  Going back here, for this 9 we need to have 6 plus 3.  To make 8 we have to have 3 plus 5.  And 5 plus 4 does make 9.  So the number in the green circle is 4. That's the answer here. Green circle is 4. That's answer D.

Video Summary

Summary Not Available