Making equations

[Sabi]

Would really appreciate some guidance on this question. Admittedly I'm not very good at it or just don't understand what I'm doing.

In a quality control process to check a batch of parts the number of acceptable parts is (x), the number of rejected parts is (y) and the % of acceptable parts for the whole batch is (k)

a)Setup an equation for (k)

b) if 60% of rejected parts can be fixed has to be scrapped which is (z), setup an equation for (z)

If 60% of rejected parts can be fixed and z is the number of rejected which must be scrapped. Setup an equation for z ............[edited]

c) determine (z) if (x)=850 and (k)=85%

So for a) I've come to.. x(x+y/100)

For b) I've come to (40y/100)=z

For c) I'm abit lost. As the numbers are too extreme so I must have done the first stages wrong.

Thanks for any pointers.

 

[Steven G]

Part a. There are x acceptable parts and y unacceptable parts. So in all there are how many parts are there? What fraction of the parts are acceptable? How do you convert that fraction to a percentage?

 

[Sabi]

There are a total of x + y parts.

The fraction of acceptable parts would be x / (x + y)

Fraction to percentage = ( x / (x+y) ) × 100 = k

Is this what you had in mind? For part a) it seems like an alternate way to get the same as what I what I came up

 

[Steven G]

It should be (x/(x+y))*100%

I divided x by x+y and then multiplied by 100%. You multiplied x by x+y and then divided by 100. Those are not the same!

For example is (25/50)*100 = (25*50)/100?

 

[Sabi]

It should be (x/(x+y))*100%

I divided x by x+y and then multiplied by 100%. You multiplied x by x+y and then divided by 100. Those are not the same!

For example is (25/50)*100 = (25*50)/100?

Ah damn yeah I get it now after plugging in numbers. How about b) don't even know how to start. Just a tip would be helpful, I'm not looking to get my work done. Feeling really dumb!

Thanks

 

[Steven G]

z=60% of rejected parts.
Wherever you see % it means divide by 100. Wherever you see of it means to multiply. Wherever you see rejected parts it means ...

 

[Sabi]

z=60% of rejected parts.
Wherever you see % it means divide by 100. Wherever you see of it means to multiply. Wherever you see rejected parts it means ...

Sorry I wrote out the question wrong...

If 60% of rejected parts can be fixed and z is the number of rejected which must be scrapped. Setup an equation for z

 

[Steven G]

Sorry I wrote out the question wrong...

If 60% of rejected parts can be fixed and z is the number of rejected which must be scrapped. Setup an equation for z

OK, fine, then still answer my question: Wherever you see rejected parts it means??

 

[Sabi]

OK, fine, then still answer my question: Wherever you see rejected parts it means??

Minus

 

[Deleted member 4993]

Would really appreciate some guidance on this question. Admittedly I'm not very good at it or just don't understand what I'm doing.

In a quality control process to check a batch of parts the number of acceptable parts is (x), the number of rejected parts is (y) and the % of acceptable parts for the whole batch is (k)

a)Setup an equation for (k)

b) if 60% of rejected parts can be fixed which is (z) setup an equation for (z)

c) determine (z) if (x)=850 and (k)=85%

So for a) I've come to.. x(x+y/100)

For b) I've come to (40y/100)=z

For c) I'm abit lost. As the numbers are too extreme so I must have done the first stages wrong.

Thanks for any pointers.

a)Setup an equation for (k)......................................\(\displaystyle k = \frac{x}{x+y} *100\) or write it as k = x/(x + y) * 100

b) if 60% of rejected parts can be fixed which is (z) setup an equation for (z)

# of rejected parts that can be fixed z = (0.6) * y​

​

# of rejected parts that cannot be fixed z = (0.4) * y​

c) determine (z) if (x)=850 and (k)=85%

continue.....

 

[Steven G]

Minus

No, it will be some variable. Which one?

 

[Sabi]

a)Setup an equation for (k)......................................\(\displaystyle k = \frac{x}{x+y} *100\) or write it as k = x/(x + y) * 100

b) if 60% of rejected parts can be fixed which is (z) setup an equation for (z)

# of rejected parts that can be fixed z = (0.6) * y​

​

# of rejected parts that cannot be fixed z = (0.4) * y​

c) determine (z) if (x)=850 and (k)=85%

continue.....

850 = x = acceptable parts
K=85%
1000 = 100%
Therefore y = 150

On the assumption that part c is also saying 60% of parts can be fixed. (I think that's what was throwing me)

Z=0.4(150)
Z=60

 

[Deleted member 4993]

850 = x = acceptable parts
K=85%
1000 = 100%
Therefore y = 150

On the assumption that part c is also saying 60% of parts can be fixed. (I think that's what was throwing me)

Z=0.4(150)
Z=60

You said

On the assumption that part c is also saying 60% of (REJECTED) parts can be fixed. (I think that's what was throwing me)

Z=0.4(150)...... Incorrect - it should be Z=0.6 (150)
Z=60 90

continue......

 

[Sabi]

You said

On the assumption that part c is also saying 60% of (REJECTED) parts can be fixed. (I think that's what was throwing me)

Z=0.4(150)...... Incorrect - it should be Z=0.6 (150)
Z=60 90

continue......

Part c is finding the value of rejected part that must be scrapped so it would be 40%?

 

[Deleted member 4993]

Part c is finding the value of rejected part that must be scrapped so it would be 40%?

You are correct - you had changed your original question.

So your response in #12 is CORRECT

 

[Sabi]

You are correct - you had changed your original question.

Yeah sorry, I wrote it out wrong and it was too late to edit. I mentioned it somewhere in the thread. Many thanks for you help.