The weights of copper and zinc in an alloy are in the ratio 8:5.
a)If the alloy contains 80g of copper, how much zinc does it contain?
b)If the alloy weights 39g, what are the weights of copper and zinc in it?
(贈送20點)..........maths
2008-03-28 4:48 am
回答 (2)
2008-03-28 4:53 am
✔ 最佳答案
a) the weight of zinc=80x5/8=50g
b) the weight of copper=39x8/(8+5)
=39x8/13
=24g
the weight of zinc=39x5/(8+5)
=39x5/13
=15g
2008-03-31 9:16 am
Let weight of copper = C, weight of Zine = Z
i.e. C / Z = 8 / 5, C = (8/5)Z
a)
if C = 80g, then 80 = (8/5)Z
Z = (80 x 5) / 8 = 50g
b)
C + Z = 39 ..... (1)
C = (8/5)Z ...... (2)
put (2) into (1),
(8/5)Z + Z = 39
(13/5) Z = 39
Z = (39 x 5) / 13
Z = 15 ..... (3)
put (3) into (1)
C = (8/5) x 15
C = 24
so, C = 24g and Z = 15g
i.e. C / Z = 8 / 5, C = (8/5)Z
a)
if C = 80g, then 80 = (8/5)Z
Z = (80 x 5) / 8 = 50g
b)
C + Z = 39 ..... (1)
C = (8/5)Z ...... (2)
put (2) into (1),
(8/5)Z + Z = 39
(13/5) Z = 39
Z = (39 x 5) / 13
Z = 15 ..... (3)
put (3) into (1)
C = (8/5) x 15
C = 24
so, C = 24g and Z = 15g
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