In two alloys A and B, the ratio of zinc to tin is 5 : 2 and

Question

In two alloys A and B, the ratio of zinc to tin is 5 : 2 and 3 : 4 respectively. How much kg of alloy A should be mixed with 21 kg of the alloy B such that in the final mixture, the quantities of zinc are tin are equal.

A. 7
B. 14
C. 21
D. 28
E. 63

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A. 7
B. 14
C. 21
D. 28
E. 63

Posted from my mobile device

BrushMyQuant · Answer

See attached image
Let total quantity of A be 7x. (taken as 7x instead as x to make calculations easier)
From the attached figure
Total Quantity of Zinc in the mixture = Zinc in A+ Zinc in B = 5x + 9 
Total Quantity of Tin in the mixture = tin in A+ tin in B = 2x + 12
 the quantities of zinc are tin are equal
=> 5x + 9 = 2x+ 12 => 3x = 12-9 = 3
=> x = 1
So, Quantity of A = 7x = 7*1 = 7
So, Answer will be A
Hope it helps!

nick1816 · Answer

5.........3
....3.5.....
0.5.......1.5

Ratio of alloy A to alloy B in the mixture= 0.5 : 1.5 = 1: 3 = 7:21

A

gracie · Answer

let a and b=kgs of alloys A and B respectively to be mixed
5a/7+3b/7=(a+b)/2→
a=1/3b
1/3*21=7 kgs
A

hardikajmani · Answer

let a be kgs of alloy A
and b be kgs of alloy B to be mixed

\frac{5a}{7
}+\frac{ 3b}{7
}= \frac{
(a+b)}{2
}
.
.
a = \frac{1}{3b
}
.
.
\frac{1}{3
} * 21 = 7 kgs

Option A

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twobagels · Answer

In alligation solution above, how did you choose 3.5?

The solution is great, but I can't figure that out. thank you

cherr012 · Answer

5x+3y = 2x +4y 
(x is for A and y is for B)

I am getting till 3x = y 
If I plug in 21 then 3x21 = 63

Where I am going wrong?

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farazmurtaza · Answer

The 21 kg of allow must contain 9kg of a and 12 kg of b.. 
So we are going to add b such in a way that.
A option which will gonna be in ratio of 5:2. 
So that

9+5 : 12+2
14 : 14

Solving without equation will be much easy.

Basshead · Answer

We know given 21 kg of B that:

9 kg is zinc and 12 kg is tin.

Lets look at the answer choices.

(A) 7. The ratio of A is 5:2. Lets try this answer out

9 + 5: 12 +2
14: 14

Answer is A.

nick1816 · Answer

Since (5+2)=(3+4) = 7, I considered the weight of their mixture = LCM(7,7)=7. Amount of zinc and tin=3.5 in mixture.

Kinshook · Answer

Given: In two alloys A and B, the ratio of zinc to tin is 5 : 2 and 3 : 4 respectively. 
Asked: How much kg of alloy A should be mixed with 21 kg of the alloy B such that in the final mixture, the quantities of zinc are tin are equal.

In 21 kg of alloy B: 
Zinc = 9 kg
Tin = 12 kg

In 7k kg of alloy A: 
Zinc = 5k kg
Tin = 2k kg

9 + 5k = 12 + 2k
3k = 3
k = 1

IMO A

In two alloys A and B, the ratio of zinc to tin is 5 : 2 and

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GMAT Problem Solving (PS) Questions

In two alloys A and B, the ratio of zinc to tin is 5 : 2 and

Prep Toolkit

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My Rewards