One alloy contains 40% and the other 20% silver. How many kg of the second alloy do you need to add to 20 kg

One alloy contains 40% and the other 20% silver. How many kg of the second alloy do you need to add to 20 kg of the first, so that after fusion together to obtain an alloy containing 36% silver?

To solve this problem, we introduce a conditional variable “X”, through which we denote the number of kilograms of the second alloy, which must be added to the first alloy.

Then, based on the data of the problem, we will compose the following equation: (0.4 x 20 + 0.2 x X) / (20 + X) = 0.36.

Solving this equation, we get 8 + 0.2X = 0.36 x (20 + X) or 8 + 0.2X = 7.2 + 0.36X or 0.8 = 0.16X or X = 5 kilograms of the second alloy.

Therefore, the correct answer is 1.5 kilograms.

Answer: 5 kilograms.