VeritasKarishma wrote:
You can easily use the scale method here. The scale method is explained here:
https://gmatclub.com/forum/tough-ds-105651.html#p828579Focus on any one of the two elements say Gold.
First bar has 2/5 gold. Second bar has 3/10 gold and mixture has 5/16 gold.
Make the fractions comparable for easy calculation i.e. give them the same denominator. LCM of 5, 10 and 16 is 80.
First bar has 32/80 gold. Second bar has 24/80 gold and mixture has 25/80 gold.
Attachment:
Ques3.jpg
So first bar weight:second bar weight should be in the ratio 1:7. Out of 8 total kgs, first bar must have been 1 kg.
Quote:
Hi Karishma,
For the scale method can we use gold to silver ratios rather than gold to total and work this problem out?
I understand in this case gold to total is an easier fraction to work with but trying to understand possibilities in scale method
No, you cannot use gold/silver ratio.
Gold/Total is the gold concentration (C1 and C2) in bar1 and bar2. You are finding the gold concentration in the two bars combined using volume as the weight of the weighted average.
Cavg = (C1 * Volume of bar1 + C2 * Volume of bar2) / (Total volume of the two bars)
Cavg = (Amount of gold in bar1 + Amount of gold in bar2) / (Total volume of the two bars)
So you can work with either gold concentration or silver concentration but not with gold/silver ratio. It doesn't give you any concentration.
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