126. Two alloys are both made up of copper and tin. The ratio of copper and tin in the first alloy is 1 : 3 and in the second alloy is 2 : 5. In what ratio should the two alloys be mixed to obtain a new alloy in which the ratio of tin and copper be 8 : 3 ?

1. 1. 3 : 5

   
   
   

   2. 4 : 7

   
   
   

   3. 3 : 8

   
   
   

   4. 5 : 11

   
   
   

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   Required ratio =	1	:	1	= 4 : 7
   	77		44

   Correct Option: B

   
   

   Required ratio =	1	:	1	= 4 : 7
   	77		44

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127. A mixture contains alcohol and water in the ratio 4 : 3. If 5 litres of water is added to the mixture, the ratio becomes 4 : 5. The quantity of alcohol in the given mixture is

1. 1. 3 litres

   
   
   

   2. 4 litres

   
   
   

   3. 15 litres

   
   
   

   4. 10 litres

   
   
   

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1. View Hint View Answer Discuss in Forum

   In original mixture,
   Alcohol = 4x litres
   Water = 3x litres
   On adding 5 litres of water,
   

   4x	=	4
   3x + 5		5

   
   ⇒  20x = 12x + 20
   ⇒  8x = 20
   

   ⇒  x =	20	=	5
   	8		2

   
   ⇒  Quantity of alcohol
   

   = 4x = 4 ×	5
   	2

   
   = 10 litres

   Correct Option: D

   In original mixture,
   Alcohol = 4x litres
   Water = 3x litres
   On adding 5 litres of water,
   

   4x	=	4
   3x + 5		5

   
   ⇒  20x = 12x + 20
   ⇒  8x = 20
   

   ⇒  x =	20	=	5
   	8		2

   
   ⇒  Quantity of alcohol
   

   = 4x = 4 ×	5
   	2

   
   = 10 litres

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128. In two alloys A and B, the ratio of zinc to tin is 5 : 2 and 3 : 4 respectively. Seven kg of the alloy A and 21 kg of the alloy B are mixed together to form a new alloy. What will be the ratio of zinc and tin in the new alloy ?

1. 1. 2 : 1

   
   
   

   2. 1 : 2

   
   
   

   3. 2 : 3

   
   
   

   4. 1 : 1

   
   
   

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1. View Hint View Answer Discuss in Forum

   In 7 kg of alloy A,
   Zinc = 5 kg, Tin = 2 kg
   In 21 kg of alloy B
   

   Zinc =	21 × 3	= 9 kg
   	7

   
   

   Tin =	21 × 4	= 12 kg
   	7

   
   ∴  Required ratio
   = (5 + 9) : (2 + 12) = 14 : 14
   or 1 : 1

   Correct Option: D

   In 7 kg of alloy A,
   Zinc = 5 kg, Tin = 2 kg
   In 21 kg of alloy B
   

   Zinc =	21 × 3	= 9 kg
   	7

   
   

   Tin =	21 × 4	= 12 kg
   	7

   
   ∴  Required ratio
   = (5 + 9) : (2 + 12) = 14 : 14
   or 1 : 1

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129. Zinc and copper are in the ratio 5 : 3 in 400 gm of an alloy. How much of copper (in grams) should be added to make the ratio 5 : 4?

1. 1. 50

   
   
   

   2. 66

   
   
   

   3. 72

   
   
   

   4. 200

   
   
   

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   In 400 gm of alloy,
   

   Zinc =	5	× 400 = 250 gm.
   	8

   
   

   Copper =	3	× 400 = 150 gm.
   	8

   
   If x gm of copper be mixed, then
   

   250	=	5
   150 + x		4

   
   ⇒  750 + 5x = 1000
   ⇒  5x = 1000 – 750 = 250
   ⇒  x = 50 gm

   Correct Option: A

   In 400 gm of alloy,
   

   Zinc =	5	× 400 = 250 gm.
   	8

   
   

   Copper =	3	× 400 = 150 gm.
   	8

   
   If x gm of copper be mixed, then
   

   250	=	5
   150 + x		4

   
   ⇒  750 + 5x = 1000
   ⇒  5x = 1000 – 750 = 250
   ⇒  x = 50 gm

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130. Two vessels A and B contain milk and water mixed in the ratio 8 : 5 and 5 : 2 respectively. The ratio in which these two mixtures be mixed to get a new mixture containing

     69	3	% milk is:
     	13

1. 1. 3 : 5

   
   
   

   2. 5 : 2

   
   
   

   3. 5 : 7

   
   
   

   4. 2 : 7

   
   
   

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1. View Hint View Answer Discuss in Forum

   Milk in the resulting mixture =	9
   	13

   
   
   

   =	65 − 63	=	2
   	7 × 13		7 × 13

   
   

   ∴   Required ratio =	2	:	1
   	7 × 13		13

   
   = 2 : 7

   Correct Option: D

   Milk in the resulting mixture =	9
   	13

   
   
   

   =	65 − 63	=	2
   	7 × 13		7 × 13

   
   

   ∴   Required ratio =	2	:	1
   	7 × 13		13

   
   = 2 : 7

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