Difference between revisions of "2024 AMC 8 Problems/Problem 4"

Latest revision as of 22:46, 4 March 2024

1 Problem
2 Solution 1
3 Video Solution 1 (Simple and Fast) by Parshwa
4 Video Solution 2 (easy to digest) by Power Solve
5 Video Solution by Math-X (First fully understand the problem!!!)
6 Video Solution by NiuniuMaths (Easy to understand!)
7 Video Solution 2 by SpreadTheMathLove
8 Video Solution by CosineMethod [🔥Fast and Easy🔥]
9 Video Solution by Intersigation
10 See Also

Problem

When Yunji added all the integers from $1$ to $9$ , she mistakenly left out a number. Her incorrect sum turned out to be a square number. What number did Yunji leave out?

$\textbf{(A) } 5\qquad\textbf{(B) } 6\qquad\textbf{(C) } 7\qquad\textbf{(D) } 8\qquad\textbf{(E) } 9$

Solution 1

The sum of the digits from $1-9$ are $1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 45$ . Note that one of the answer choices (that is equal to Yunju's digits) subtracted from her sum of $45$ must equal a square.

Note that $6^2 = 36$ is a very close square to the sum of 45. Checking, we see that $45 - 9 = 36 = 6^2$ works.

Therefore, the missing number is $\boxed{\textbf{(E) } \text{9}}$ .

Video Solution 1 (Simple and Fast) by Parshwa

https://youtu.be/Qrf4GTDjjXs

Video Solution 2 (easy to digest) by Power Solve

https://youtu.be/HE7JjZQ6xCk?si=sTC7YNSmfEOMe4Sn&t=179

Video Solution by Math-X (First fully understand the problem!!!)

https://youtu.be/BaE00H2SHQM?si=9ZUxEGmGam7il9xr&t=907

~Math-X

Video Solution by NiuniuMaths (Easy to understand!)

https://www.youtube.com/watch?v=Ylw-kJkSpq8

~NiuniuMaths

Video Solution 2 by SpreadTheMathLove

https://www.youtube.com/watch?v=L83DxusGkSY

Video Solution by CosineMethod [🔥Fast and Easy🔥]

noooooooooooooooooooooooooooooooooooooo!!!!!!!!!!!!!!!!!!

Video Solution by Intersigation

https://youtu.be/ktzijuZtDas&t=232

@@ Line 2: / Line 2: @@
 When Yunji added all the integers from <math>1</math> to <math>9</math>, she mistakenly left out a number. Her incorrect sum turned out to be a square number. What number did Yunji leave out?
-<math>Yunji is dumb</math>
+<math>\textbf{(A) } 5\qquad\textbf{(B) } 6\qquad\textbf{(C) } 7\qquad\textbf{(D) } 8\qquad\textbf{(E) } 9</math>
-🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦
+==Solution 1==
-🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦⬛⬛🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦⬛⬛🟦🟦🟦🟦🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦🟦🟦🟦⬛⬛⬛🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦⬛⬛⬛🟦🟦🟦🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛🟦🟦🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛🟦🟦🟦🟦⬛⬛🟦🟦🟦⬛⬛🟦🟦🟦🟦⬛⬛⬛⬛🟦🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛🟦🟦⬛⬛⬛⬛🟦⬛⬛⬛⬛🟦🟦⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦⬛⬛⬛⬛⬛🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦
-🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦
-🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦
-🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦
-🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦
-🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦
-🟦⬛⬛⬛🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦⬛⬛🟦
-🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦
-🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦
-🟦🟦⬛⬛⬛⬛⬛⬛⬛🟩🟩⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟩🟩⬛⬛⬛⬛⬛⬛⬛🟦🟦
-🟦🟦🟦⬛⬛⬛⬛⬛🟩🟩⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟩🟩⬛⬛⬛⬛⬛🟦🟦🟦
-🟦🟦🟦🟦⬛⬛⬛⬛🟩🟩⬛⬜⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬜⬛🟩🟩⬛⬛⬛⬛🟦🟦🟦🟦
-🟦🟦🟦⬛⬛⬛⬛⬛⬛🟩⬛⬛⬛⬛🟩⬛⬛⬛⬛⬛⬛🟩⬛⬛⬛⬛🟩⬛⬛⬛⬛⬛⬛🟦🟦🟦
-🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛🟩⬛⬛🟩🟩⬛⬛⬛⬛⬛⬛🟩🟩⬛⬛🟩⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦
-🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦
-🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦⬛⬛⬛⬛⬛⬛🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦
-🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦🟦
-==wapjgpoaewhgawehgoihewoighoiwhg[owrh[oigawh[oghw[aw==
+The sum of the digits from <math>1-9</math> are <math>1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 45</math>. Note that one of the answer choices (that is equal to Yunju's digits) subtracted from her sum of <math>45</math> must equal a square.
-Roses are red
-violets are blue
+Note that <math>6^2 = 36</math> is a very close square to the sum of 45. Checking, we see that <math>45 - 9 = 36 = 6^2</math> works.
-Grass is green
+Therefore, the missing number is <math>\boxed{\textbf{(E) } \text{9}}</math>.
-Chair
+==Video Solution 1 (Simple and Fast) by Parshwa==
+https://youtu.be/Qrf4GTDjjXs
-==Solution 3==
+==Video Solution 2 (easy to digest) by Power Solve==
-Recall from AMC12A 2022 Problem 16, that <math>1+2+\dots+8 = 6^2</math>. Hence removing <math>9</math> works and our answer is <math>\boxed{\textbf{(E) }9}</math>.
--iamcalifornia'sresidentidiot
-==Solution 4==
-using the theory of relativity, 1+5 is 4 so therefore Mark Zuckerburg is a lizard person and the earth is actually flat, which proves the pythagorean theorom
--by random_uwu_gamer_girl
-BAN ME I DARE YOU I ACTUALLY DARE
-==Video Solution 1 (easy to digest) by Power Solve==
 https://youtu.be/HE7JjZQ6xCk?si=sTC7YNSmfEOMe4Sn&t=179
@@ Line 74: / Line 34: @@
 == Video Solution by CosineMethod [🔥Fast and Easy🔥]==
-https://www.youtube.com/watch?v=9v5q5DxeriM
+noooooooooooooooooooooooooooooooooooooo!!!!!!!!!!!!!!!!!!
 ==Video Solution by Intersigation==
 https://youtu.be/ktzijuZtDas&t=232

2024 AMC 8 (Problems • Answer Key • Resources)
Preceded by Problem 3	Followed by Problem 5
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25
All AJHSME/AMC 8 Problems and Solutions

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