A zinc-copper alloy contains 1,280 grams less zinc, and after removing 60% zinc and 30% copper from the alloy, the weight is 1,512 grams. Find the initial mass of the alloy
Let us denote the weight of zinc in the alloy through q, and the weight of copper through m. Then we compose the following equalities, but first the record that 60% of zinc was removed from the alloy means that 0.4 weight of zinc remains.
Likewise with copper, since 30 percent was removed, 0.7 of the original weight of copper remains.
m + 1280 = c; 0.4 * q + 0.7 * m = 1512;
0.4 * (m + 1280) + 0.7 * m = 1512.4.4 * m + 0.7 * m + 512 = 1512;
1.1 * m = 1000; m = 1000: 1.1 = 909.1 (gram) – there was copper.
Zinc was 909.1 + 1280 = 2189.1 (gram).
0.4 * 2189.1 + 0.7 * 909.1 = 875.6 + 636.4 = 1512.
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