mohshu wrote:

@vertasprepkarishma

any way to get this done by weighted avg method

Hi Mohshu,

The algebraic approach is the best way to solve this problem as it requires a basic understand of percentages. If we keep the the weight of iron as

'x' grams, the total alloy will weigh

'387+x' grams. Since copper makes up 90% of the alloy,

387/(387+x) = 90/100Simplifying we get x =

43gramsThe alternate approach is to make use of the alligation approach. To use the alligation approach there are two things that you need to do.

1. Draw the alligation diagram the basic framework of which is given belowAttachment:

Mixtures 1.png [ 8.12 KiB | Viewed 949 times ]
2. Make sure that the values you substitute as the higher value, lower value and mean value are values associated with the word 'per' (percentages, ratios, averages...)Now in this question we can form an alligation diagram using the percentages of Copper, we get the higher value as 100% and the lower value as 0%, since we have pure copper and pure iron respectively (the percentage of copper in pure iron is 0%)

Attachment:

Untitled.png [ 7.48 KiB | Viewed 950 times ]
Since the ratio of copper to iron in the alloy is 9 : 1 and the weight of copper is 387 grams, then this 387 grams represents 9 parts of the ratio. So the weight of iron which is represented by 1 part in the ratio will be 387/9 =

43gramsHope this helps!

CrackVerbal Academics Team

_________________

Join Free 4 part MBA Through GMAT Video Training Series here -

https://gmat.crackverbal.com/mba-through-gmat-video-2018

Enroll for our GMAT Trial Course here -

http://gmatonline.crackverbal.com/

For more info on GMAT and MBA, follow us on @AskCrackVerbal