How to solve a percentage word problem for profit?

[alijan kk]

Homework Statement

A person lost 10% when he sold goods at Rs 153 for how much should he sell them to gain 20% .

Homework Equations

The Attempt at a Solution

0.10(153)= 15.3

153+15.3= 168.3 ( the price of product for no profit)

0.2(168.3)=33.6
(168.3+33.6)= 201.9 rupees is the 20% gain ?

have i done the problem correctly , or is their a more general way to do this.

 

[phinds]

In your first step, you have taken 10% of the sale amount. Is that really what you want to be doing? Think about it.

 

[alijan kk]

In your first step, you have taken 10% of the sale amount. Is that really what you want to be doing? Think about it.

negative 10 percent ?

 

[FactChecker]

negative 10 percent ?
IS MY ANS CORRECT?

No. You are taking 10% of the wrong thing. @phinds hint is a good one.
EDIT: I would have been more clear if I said that you are using 10% the wrong way.

 

[berkeman]

negative 10 percent ?
IS MY ANS CORRECT?

No, it is not correct (and no need to be yelling with all capital letters...).

As @phinds was hinting, your original method to calculate the starting amount is not correct (you have made a very common error for students learning to work this type of problem.

If I have 100 of something, what is 10% less than that? Can you apply that same logic to this problem? Let X be the starting amount in this problem, and try again to do the calculation, using the hint I have provided.

Dang it, beaten out y @FactChecker yet again...

 

[alijan kk]

No, it is not correct (and no need to be yelling with all capital letters...).

As @phinds was hinting, your original method to calculate the starting amount is not correct (you have made a very common error for students learning to work this type of problem.

If I have 100 of something, what is 10% less than that? Can you apply that same logic to this problem? Let X be the starting amount in this problem, and try again to do the calculation, using the hint I have provided.

Dang it, beaten out y @FactChecker yet again...

i am sorry i still don't get it :(

 

[berkeman]

If I have 100 of something, what is 10% less than that? Can you apply that same logic to this problem? Let X be the starting amount in this problem

Use my hint. Let X be the starting amount, and Y is the amount that is discounted by 10%. Show that equation please. Then let Z be the amount that is 20% more than the starting amount. Can you show that equation please?

Then using those two equations that you have written out, you should be able to solve the problem with a little algebraic manipulation...

Please show all of your work so we can check it. Thank you.

 

[alijan kk]

Use my hint. Let X be the starting amount, and Y is the amount that is discounted by 10%. Show that equation please. Then let Z be the amount that is 20% more than the starting amount. Can you show that equation please?

Then using those two equations that you have written out, you should be able to solve the problem with a little algebraic manipulation...

Please show all of your work so we can check it. Thank you.

0.90X=Y

is this a correct equation

 

[berkeman]

0.90X=Y

is this a correct equation

Yes, good so far! Keep on going...

 

[alijan kk]

Yes, good so far! Keep on going...

original price is 170 !
yes thankyou . i am going.. not very well but ok

 

[alijan kk]

Use my hint. Let X be the starting amount, and Y is the amount that is discounted by 10%. Show that equation please. Then let Z be the amount that is 20% more than the starting amount. Can you show that equation please?

Then using those two equations that you have written out, you should be able to solve the problem with a little algebraic manipulation...

Please show all of your work so we can check it. Thank you.

Z= 170+0.20(170)= 204 yes this is the answer thankyou!

 

[berkeman]

Z= 170+0.20(170)= 204 yes this is the answer thankyou!

Good work.

So do you see the issue now with your original approach? You need to find the original value before trying to add to it. Like I said, it is a common error as you start to learn this type of problem. But now you know what to look out for!

 

[berkeman]

Z= 170+0.20(170)= 204 yes this is the answer thankyou!

BTW, another way to write that is 1.2 * 170 = 204.

 

[alijan kk]

BTW, another way to write that is 1.2 * 170 = 204.

hmm yes direct answer

 

[alijan kk]

hmm yes direct answer

i am sorry to post here , but i how can i use all maths symbol ? (to post calculus problems)

 

[berkeman]

i am sorry to post here , but i how can i use all maths symbol ? (to post calculus problems)

No worries, and good for you to want to start posting using math symbols. You can click on the sigma ∑ symbol in the toolbar at the top of the Edit window to get simple symbols for in-line text, and you can learn more about posting in LaTeX in the tutorial under INFO/Help-How To at the top of the page.