Grades 3-4 Video Solutions 2021-video 2021 3-4/23

Video Transcription

Problem number 23. Elena wants to write the numbers from 1 to 9 in the square shown. The arrows always point from a smaller number to a larger one. She has already written 5 and 7.  Which number should she write instead of the question mark? A2, B3, C4, D6, or E8? The largest number, which is 9, will go in the square to which the arrows end up pointing.  Well, here's 7, and there are 2 arrows pointing from it, and also there are 2 other arrows pointing to this square.  So, since the numbers have to go up, the 8 will be here, and the 9 will be here.  Then, the smallest number has to go in the square from which all the arrows are pointing, which is right here.  These 4 numbers all have to be less than 5, so we will have 1, 2, 3, and 4 here.  The 4 has to go here, but the 2 and the 3 can go in either one of these two and still keep the rules. She leaves only the number 6 to be placed in this square, so the answer is D6.

Video Summary

Elena needs to place numbers 1 to 9 in a square grid where arrows point from smaller to larger numbers. Given that 5 and 7 are already placed, and 9 must be the largest number, it is concluded that 8 and 9 go in the final two squares with arrows pointing towards them. The smallest number, 1, must be at the starting point where all arrows originate. Since numbers 1, 2, 3, and 4 must be less than 5, 4 is specifically placed, leaving 6 as the only number that fits in the remaining square with the question mark. Thus, the answer is D6.