Difference between revisions of "2024 AMC 10A Problems/Problem 7"
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− | The | + | {{duplicate|[[2024 AMC 10A Problems/Problem 7|2024 AMC 10A #7]] and [[2024 AMC 12A Problems/Problem 6|2024 AMC 12A #6]]}} |
+ | |||
+ | ==Problem== | ||
+ | The product of three integers is <math>60</math>. What is the least possible positive sum of the | ||
+ | three integers? | ||
+ | |||
+ | <math>\textbf{(A) }2\qquad\textbf{(B) }3\qquad\textbf{(C) }5\qquad\textbf{(D) }6\qquad\textbf{(E) }13</math> | ||
+ | |||
+ | ==Solution 1== | ||
+ | We notice that the optimal solution involves two negative numbers and a positive number. Thus we may split <math>60</math> into three factors and choose negativity. We notice that <math>10\cdot6\cdot1=10\cdot(-6)\cdot(-1)=60</math>, and trying other combinations does not yield lesser results so the answer is <math>10-6-1=\boxed{\textbf{(B) }3}</math>. | ||
+ | |||
+ | ~eevee9406 | ||
+ | |||
+ | == Solution 2== | ||
+ | We have <math>abc = 60</math>. Let <math>a</math> be positive, and let <math>b</math> and <math>c</math> be negative. Then we need <math>a > |b + c|</math>. If <math>a = 6</math>, then <math>|b + c|</math> is at least <math>7</math>, so this doesn't work. If <math>a = 10</math>, then <math>(b,c) = (-6,-1)</math> works, giving <math>10 - 7 = \boxed{\textbf{(B) }3}</math> | ||
+ | |||
+ | ~[[User:pog|pog]],~[[User:Mathkiddus|mathkiddus]] | ||
+ | |||
+ | == Solution 3 == | ||
+ | We can see that the most optimal solution would be <math>1</math> positive integer and <math>2</math> negative ones (as seen in solution 1). Let the three integers be <math>x</math>, <math>y</math>, and <math>z</math>, and let <math>x</math> be positive and <math>y</math> and <math>z</math> be negative. If we want the optimal solution, we want the negative numbers to be as large as possible. so the answer should be <math>-60 \cdot -1 \cdot 1</math>, where <math>-60 - 1 + 1 = -60</math>... right? | ||
+ | |||
+ | No! Our sum must be a positive number, so that would be invalid! We see that -<math>30, -20, -15</math>, and <math>-10</math> are too far negative to allow the sum to be positive. For example, <math>-15 = z. -15xy=60</math>, so <math>xy = -4</math>. For <math>xy</math> to be the most positive, we will have <math>4</math> and <math>-1</math>. Yet, <math>-15+4-1</math> is still less than <math>0</math>. After <math>-10</math>, the next factor of <math>60</math> would be <math>6</math>. if <math>z</math> = <math>-6</math>, <math>xy = -10</math>. This might be positive! Now, if we have <math>z = -6, y = -1</math>, and <math>x = 10, x + y + z = 3</math>. It cannot be smaller because <math>x = 5</math> and <math>y = -2</math> would result in <math>x + y + z</math> being negative. Therefore, our answer would be <math>\boxed{\textbf{(B) }3}</math>. | ||
+ | |||
+ | ~Moonwatcher22 | ||
+ | |||
+ | == Video Solution by Pi Academy == | ||
+ | |||
+ | https://youtu.be/6qYaJsgqkbs?si=K2Ebwqg-Ro8Yqoiv | ||
+ | |||
+ | == Video Solution 1 by Power Solve == | ||
+ | https://youtu.be/j-37jvqzhrg?si=aggRgbnyZ3QjYwZF&t=806 | ||
+ | |||
+ | == Video Solution by Daily Dose of Math == | ||
+ | |||
+ | https://youtu.be/e8eL1l5os30 | ||
+ | |||
+ | ~Thesmartgreekmathdude | ||
+ | |||
+ | ==See also== | ||
+ | {{AMC10 box|year=2024|ab=A|num-b=6|num-a=8}} | ||
+ | {{AMC12 box|year=2024|ab=A|num-b=5|num-a=7}} | ||
+ | {{MAA Notice}} |
Latest revision as of 20:18, 9 November 2024
- The following problem is from both the 2024 AMC 10A #7 and 2024 AMC 12A #6, so both problems redirect to this page.
Contents
Problem
The product of three integers is . What is the least possible positive sum of the three integers?
Solution 1
We notice that the optimal solution involves two negative numbers and a positive number. Thus we may split into three factors and choose negativity. We notice that , and trying other combinations does not yield lesser results so the answer is .
~eevee9406
Solution 2
We have . Let be positive, and let and be negative. Then we need . If , then is at least , so this doesn't work. If , then works, giving
Solution 3
We can see that the most optimal solution would be positive integer and negative ones (as seen in solution 1). Let the three integers be , , and , and let be positive and and be negative. If we want the optimal solution, we want the negative numbers to be as large as possible. so the answer should be , where ... right?
No! Our sum must be a positive number, so that would be invalid! We see that -, and are too far negative to allow the sum to be positive. For example, , so . For to be the most positive, we will have and . Yet, is still less than . After , the next factor of would be . if = , . This might be positive! Now, if we have , and . It cannot be smaller because and would result in being negative. Therefore, our answer would be .
~Moonwatcher22
Video Solution by Pi Academy
https://youtu.be/6qYaJsgqkbs?si=K2Ebwqg-Ro8Yqoiv
Video Solution 1 by Power Solve
https://youtu.be/j-37jvqzhrg?si=aggRgbnyZ3QjYwZF&t=806
Video Solution by Daily Dose of Math
~Thesmartgreekmathdude
See also
2024 AMC 10A (Problems • Answer Key • Resources) | ||
Preceded by Problem 6 |
Followed by Problem 8 | |
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 AMC 10 Problems and Solutions |
2024 AMC 12A (Problems • Answer Key • Resources) | |
Preceded by Problem 5 |
Followed by Problem 7 |
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 AMC 12 Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.