Art of Problem Solving

2025 AMC 10A Problems/Problem 2: Difference between revisions

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<imath>\textbf{(A)}~3.5\qquad\textbf{(B)}~4\qquad\textbf{(C)}~4.5\qquad\textbf{(D)}~5\qquad\textbf{(E)}~6</imath>
<imath>\textbf{(A)}~3.5\qquad\textbf{(B)}~4\qquad\textbf{(C)}~4.5\qquad\textbf{(D)}~5\qquad\textbf{(E)}~6</imath>


==Solution 1==
==Solution ==
Since the first box had 5 pounds, and 50 percent of it had peanuts, we know there were 5 pounds of peanuts at the beginning.   
Since the first box had 5 pounds, and 50 percent of it had peanuts, we know there were 5 pounds of peanuts at the beginning.   



Revision as of 16:38, 6 November 2025

The following problem is from both the 2025 AMC 10A #2 and 2025 AMC 12A #2, so both problems redirect to this page.

Problem

A box contains $10$ pounds of a nut mix that is $50$ percent peanuts, $20$ percent cashews, and $30$ percent almonds. A second nut mix containing $20$ percent peanuts, $40$ percent cashews, and $40$ percent almonds is added to the box resulting in a new nut mix that is $40$ percent peanuts. How many pounds of cashews are now in the box?

$\textbf{(A)}~3.5\qquad\textbf{(B)}~4\qquad\textbf{(C)}~4.5\qquad\textbf{(D)}~5\qquad\textbf{(E)}~6$

Solution

Since the first box had 5 pounds, and 50 percent of it had peanuts, we know there were 5 pounds of peanuts at the beginning.

Adding the second mixture of nuts, we call this value $x$, as in $x$ pounds. Of that, 20%, or $\frac{x}{5}$, are peanuts.

Since the final percentage is 40 percent peanuts, we have \[\frac{5 + \frac{x}{5}}{10 + x} = \frac{2}{5}.\]

Multiplying both sides by $5(10 + x)$, we get \[25 + x = 20 + 2x.\]

This gives us $x = 5$.

But the problem is asking us to solve for cashews.

The first mixture was $\frac{1}{5}$ cashews, so there were $2$ pounds of cashews in the first mix. In the second, there were $\frac{2x}{5}$ cashews, or 2 pounds of cashews.

Adding this together gives us a final total of \[2 + 2 = \boxed{4}\] pounds of cashews.

  • ~Minor edits to LaTeX by WildSealVM/Vincent M

See Also

2025 AMC 10A (ProblemsAnswer KeyResources)
Preceded by
Problem 1
Followed by
Problem 3
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
2025 AMC 12A (ProblemsAnswer KeyResources)
Preceded by
Problem 1
Followed by
Problem 3
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

These problems are copyrighted © by the Mathematical Association of America.