F.3 Maths(Percentage)
2008-10-12 3:52 am
An alloy A contains 35% of zinc by weight. Some alloy A and pure zinc are melted to form a new alloy that weights 400kg and contains 1057/16 % of zinc. What are the weights of alloy A and zinc needed respectively to form the new alloy? (Give your answers correct to the nearest kg.)
回答 (2)
2008-10-12 4:37 am
✔ 最佳答案
Let there are x kg and y kg of the mass of alloy A and the mass of pure zinc needed to form the new alloy respectively.x + y = 400 -------------------------------------(1)
0.35x + y = 400 (1057/16)% ------------------(2)
(2), 0.35x + y = 400 (66.0625%) ----------(3)
(1) – (3),
x + y – (0.35x + y) = 400 – 400(66.0625%)
0.65x = 400 – 264.25
0.65x = 400 – 264.25
0.65x = 135.75
x = 208.846
Sub x = 208.846 into (1),
208.846 + y = 400
y = 191.154
∴ The weights of alloy A needed to form the new alloy is 209 kg .
∴ The weights of zinc needed to form the new alloy is 191 kg .
希望幫到您！
2008-10-12 7:10 am
Let there are x kg and y kg of the mass of alloy A and the mass of pure zinc needed to form the new alloy respectively.
x + y = 400 -------------------------------------(1)
0.35x + y = 400 (1057/16)% ------------------(2)
(2), 0.35x + y = 400 (66.0625%) ----------(3)
(1) – (3),
x + y – (0.35x + y) = 400 – 400(66.0625%)
0.65x = 400 – 264.25
0.65x = 400 – 264.25
0.65x = 135.75
x = 208.846
Sub x = 208.846 into (1),
208.846 + y = 400
y = 191.154
∴ The weights of alloy A needed to form the new alloy is 209 kg .
∴ The weights of zinc needed to form the new alloy is 191 kg
I hope I can help you.
x + y = 400 -------------------------------------(1)
0.35x + y = 400 (1057/16)% ------------------(2)
(2), 0.35x + y = 400 (66.0625%) ----------(3)
(1) – (3),
x + y – (0.35x + y) = 400 – 400(66.0625%)
0.65x = 400 – 264.25
0.65x = 400 – 264.25
0.65x = 135.75
x = 208.846
Sub x = 208.846 into (1),
208.846 + y = 400
y = 191.154
∴ The weights of alloy A needed to form the new alloy is 209 kg .
∴ The weights of zinc needed to form the new alloy is 191 kg
I hope I can help you.
參考: my maths knowledge
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