Question

11. The ratio of zinc and copper in an alloy is 7:9. If
the weight of copper in the alloy is 11.7 kg, find
(1) The total weight of alloy
​

Answer 1

Answer:

Given that ratio of zinc and copper in an alloy is 7: 9

Let their ratio = 7x: 9x

Weight of copper = 11.7 kg

9x = 11.7 x = 11.7/9

x = 1.3

Weight of the zinc in the alloy = 1.3 × 7 = 9.10 kg

Answer 2

★ Given:

The ratio of zinc and copper in an alloy is 7:9.

The weight of copper in the alloy is 11.7 kg.

★ To Find:

The total weight of the alloy.

★ Solution:

We can convert the ratio of zinc and copper in the alloy to fraction as 7/9.

We know that the weight of copper is 11.7 kg.

So forming a proportion:

7:9 :: x:11.7

$\sf{\dfrac{7}{9}=\dfrac{x}{11.7}}$

By doing cross multiplication:

7 x 11.7 = 9x

81.9 = 9x

x = 81.9/9

x = 9.1

Therefore the weight of zinc in the alloy is 9.1 kg.

Now, we have two values:

The weight of copper is 11.7 kg.

The weight of zinc is 9.1 kg.

Therefore the total weight of the alloy is

11.7 kg + 9.1 kg

= 20.8 kg

Therefore the required answer is 20.8 kg.