One alloy has 30% copper, the other 70% copper. how many kilograms each alloy needs to get

| September 26, 2021 | education

One alloy has 30% copper, the other 70% copper. how many kilograms each alloy needs to get 100 kg of an alloy that has 40% copper.

Let x be the amount of 30% alloy, then the amount of 70% alloy will be equal to (100 – x), since 100 kg of 40% alloy should be obtained.

Converting percentages to decimal numbers: 30% = 0.3; 70% = 0.7; 40% = 0.4.

Let us express the amount of pure copper in a 30% alloy: 0.3x (kg)

Let us express the amount of pure copper in a 70% alloy: 0.7 (100 – x) (kg).

Let us express the amount of pure copper in the resulting 40% alloy: 100 * 0.4 = 40 (kg).

The equation turns out:

0.3x + 0.7 (100 – x) = 40.

0.3x + 70 – 0.7x = 40.

0.3x – 0.7x = 40 – 70.

-0.4x = -30.

x = -30: (-0.4) = 300: 4 = 75 (kg) – the amount of 30% alloy.

100 – 75 = 25 (kg) – the amount of 70% alloy.



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