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An alloy contains zinc, copper, and tin in the ratio 2:3:1 and another GMAT Problem Solving

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Sayantani Barman

Experta en el extranjero | Updated On - Mar 15, 2023

Question: An alloy contains zinc, copper, and tin in the ratio 2:3:1 and another contains copper, tin and lead in the ratio 5:4:3. If equal weights of both alloys are melted together to form a third alloy, then the weight of lead per kg in new alloy will be:

A. 1/10 kg
B. 1/8 kg
C. 1/6 kg
D. ¼ kg
E. ½ kg

Answer: B

Approach Solution (1):
Ratio of Zinc, Copper and Tin is given as,
Z : C : T = 2 : 3 : 1.
Now, let the first alloy be 12 kg (taken as 4 kg Zinc, 6 kg Copper and 2 Kg Lead). Weight of second alloy = 12 kg as, C : T : L = 5 : 4 : 3. (taken as 5 kg Copper, 4 kg Tin and 3 Kg Lead.)
Alloys are mixed together to form third alloy. Then the ratio of content in it,
Z : C : T : L = 4 : (6 + 5) : (2 + 4) : 3
Weight of third alloy = 12 + 12 = 24 kg
So, weight of the Lead =3/24 =1/8kg
Correct option:
B

Approach Solution (2):
The 2:3:1 alloy adds to 6 parts total, while 5:4:3 adds to 12 parts. The problem is easier if the first alloy is based on 12 parts total so we double it 4:6:2.
Now if we add equal weights, there are 24 parts total and only 3 parts from the 2nd alloy are lead. the lead is 3/24 = 1/8 part or 125 g/kg.
Correct option:
B

Approach Solution (3):
2 + 3 + 1 = 6
2 * 6 = 12
In order to have both alloys in same proportion, we need 2 kgs of 1st for every 1 kg of 2nd:
Proportion of lead = (0 + 3) / (2*6 + 12) = 3/24 = 1/8
Correct option:
B

“An alloy contains zinc, copper, and tin in the ratio 2:3:1 and another contains copper, tin and lead in the ratio 5:4:3. If equal weights of both alloys are melted together to form a third alloy, then the weight of lead per kg in new alloy will be:”- is a topic of the GMAT Quantitative reasoning section of GMAT. This question has been taken from the book “GMAT Official Guide Quantitative Review”. To solve GMAT Problem Solving questions a student must have knowledge about a good amount of qualitative skills. The GMAT Quant topic in the problem-solving part requires calculative mathematical problems that should be solved with proper mathematical knowledge.

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