Question

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?

$3.5$

$4$

$4.5$

$5$

$6$

Solution:

The starting $10$ -pound mix holds $5$ pounds of peanuts and $2$ pounds of cashews. Add $x$ pounds of the second mix, which is $20\%$ peanuts. We want the new peanut fraction to be $40\%,$ so $\frac{5 + 0.2x}{10 + x} = 0.4.$ This means $5 + 0.2x = 4 + 0.4x,$ giving $x = 5.$ Those $5$ pounds bring $0.4 \cdot 5 = 2$ more pounds of cashews, so the box now has $2 + 2 = 4.$ Therefore, the answer is B.

2025 AMC 10A Problem 2

Solution:

Problem 2 in Other Years