How do I calculate percentage increase for ratios in math homework?

[asmalik12]

Homework Statement

1. A photocpier increases the paper with the ratio 4:5, what % is the paper increased
2. An alloay has a copper, alloy and lead with the ratio 5:7:3, what % is the alloy to lead


2. The attempt at a solution

1. Difference in equation = 5 - 4 = 1
= 1/4 * 100
= 25 %

2. Difference between the ratio of alloy and lead = 7 - 3 = 4
= 4/7 * 100
= 57.14 %

Am I doing it rightly?

 

[Mark44]

Homework Statement

1. A photocpier increases the paper with the ratio 4:5, what % is the paper increased
2. An alloay has a copper, alloy and lead with the ratio 5:7:3, what % is the alloy to lead


2. The attempt at a solution

1. Difference in equation = 5 - 4 = 1
= 1/4 * 100
= 25 %

Yes, this is correct.

2. Difference between the ratio of alloy and lead = 7 - 3 = 4
= 4/7 * 100
= 57.14 %

Am I doing it rightly?

No. There are 7 parts alloy to 3 parts lead, so there is about 2.33 times as much alloy as lead.

 

[asmalik12]

For Question No. 2

Difference in the ratio of alloy to lead = 7 - 3 = 4
= 4/3 * 100
= 133.33 %

Now ?

 

[mege]

For question number two - are there 3 parts that you are comparing the 1 part to? Why does the problem refer to alloy as both the whole and a part? (I'm wondering if part of the confusion is in the presentation of the problem)

If the ratio is: ALLOY = Copper:OtherALLOY:Lead then I second Mark44's solution.