Final answer:
The total amount of alloy is found by first determining the number of parts in 15 kg of iron according to the given ratio (15kg / 5), then calculating the weight of tungsten, and finally adding the two weights together. The total weight of the alloy is 18 kg. The correct option is a).
Step-by-step explanation:
The student's question asks how much alloy there is if an alloy contains iron and tungsten in the ratio 5:1 and there are 15kg of iron in the alloy.
To answer this question, we first recognize that for every 5 kg of iron in the alloy, there must be 1 kg of tungsten, as indicated by the 5:1 ratio. Since there are 15 kg of iron, we can divide this weight by the iron ratio to find out how many parts of the alloy there are:
15kg ÷ 5 = 3 parts
Now, knowing there are 3 parts of tungsten, we can determine the total mass of the tungsten in the alloy:
3 parts × 1kg/part = 3 kg of tungsten
To find the total mass of the alloy, we add the mass of iron to the mass of tungsten:
15 kg of iron + 3 kg of tungsten = 18 kg of alloy
Therefore, the answer is 18 kg, which corresponds to option (a) 18kg.