Question

an ore contains 12% copper .How many kg of the ore are required to get 69 kg of copper

Answer 1

Let the total quantity of the ore be 'x' kg
So, 12 % of that ore is copper.
According to the question.

(x*12)/100 = 69
12x/100 = 69
3x/25 = 69
3x = 69*25
3x = 1725
x = 1725/3
x = 575 kg

So, 575 kg ore is required to get 69 kg of copper.

Answer 2

We will take the total weight of the ore as 'x'
We know that 20%of it is copper.
That means,
20% of x =69kg
=>20/100× x = 69kg
ie, 20x=69×100
=6900
X=6900/20
=345//
Verification
20/100×345
=6900/100=69