Question

Two cubes of bronze have their total weight equivalent to 60 kg. The first piece contains 10 kg of pure zinc and the second piece contains 8 kg of pure z what is the percentage of zinc in the first piece of bronze if the second piece contains 15 percent more zinc than the first ?

Answer 1

Answer:

Total weight of two cubes = 60 kg  

Let the weight of the two cubes of bronze be “x” kg and “(60 - x)” kg respectively.

Weight of zinc in the first piece = 10 kg

∴ % of pure zinc in the first piece = [10/x] * 100 = 1000/x %

And,

Weight of zinc in the second piece = 8 kg  

∴ % of pure zinc in the first piece = [8/(60 – x)] * 100 = 800/(60 – x) %

According to the question, we get

[800/(60 – x)] – [1000/x] = 15

⇒ [160/(60 – x)] – [200/x] = 3

⇒ 160x  - 12000 + 200x = 180x - 3x²  

⇒ 3x² + 180x - 12000 = 0

⇒ x² – 60x + 4000 = 0

⇒ (x+100)(x-40) = 0

⇒ x = 40  kg

Thus,  

The percentage of zinc in the first piece of bronze is

= 1000/x %

= 1000/40 %

= 25 %

Answer 2

Answer:

25%

Explanation:

suppose weight of 1st piece is x and that of 2nd piece is y

x+y = 60

and

(10/x)*100 + 15 = (8/y)*100

x=40 and y = 20

so weight of 1st piece is 40kg

percentage = (10/40)*100 = 25%