286. One type of liquid contains 20% water and the second type of liquid contains 35% of water. A glass is filled with 10 parts of first liquid and 4 parts of second liquid. The water in the new mixture in the glass is

1. 1. 37%

   
   
   

   2. 46%

   
   
   

   3. 12	1	%
      	7

   
   
   

   4. 24	2	%
      	7

   
   
   

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1. View Hint View Answer Discuss in Forum

   In 10 litres of first type of liquid,
   

   Water =	1	× 10 = 2 litres
   	5

   
   In 4 litres of second type of liquid,
   

   Water = 4 ×	35	=	7	litres
   	100		5

   
   

   Total amount of water = 2 +	7	=	17	litres
   	5		5

   
   

   Correct Option: D

   In 10 litres of first type of liquid,
   

   Water =	1	× 10 = 2 litres
   	5

   
   In 4 litres of second type of liquid,
   

   Water = 4 ×	35	=	7	litres
   	100		5

   
   

   Total amount of water = 2 +	7	=	17	litres
   	5		5

   
   

   ∴ Required percentage =	17
   	5	× 100
   	14

   
   

   Required percentage =	170	= 24	2	%
   	7		7

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287. In one litre of a mixture of alcohol and water, water is 30%. The amount of alcohol that must be added to the mixture so that the part of water in the mixture becomes 15% is :

1. 1. 1000 ml

   
   
   

   2. 700 ml

   
   
   

   3. 300 ml

   
   
   

   4. 900 ml

   
   
   

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1. View Hint View Answer Discuss in Forum

   In 1 litre i.e. 1000 ml of mixture,
   Alcohol = 700 ml.
   Water = 300 ml.
   Let m ml of alcohol is mixed.
   

   ∴	300	× 100 = 15
   	1000 + m

   
   

   Correct Option: A

   In 1 litre i.e. 1000 ml of mixture,
   Alcohol = 700 ml.
   Water = 300 ml.
   Let m ml of alcohol is mixed.
   

   ∴	300	× 100 = 15
   	1000 + m

   
   ⇒ 1000 + m = 2000
   ⇒ m = 1000 ml.

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288. How much water must be added to 100 ml of 80 per cent solution of boric acid to reduce it to a 50 per cent solution ?

1. 1. 30 ml

   
   
   

   2. 40 ml

   
   
   

   3. 50 ml

   
   
   

   4. 60 ml

   
   
   

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1. View Hint View Answer Discuss in Forum

   Let m ml of water be added.
   

   ∴	20 + m	× 100 = 50
   	100 + m

   
   

   Correct Option: D

   Let m ml of water be added.
   

   ∴	20 + m	× 100 = 50
   	100 + m

   
   ⇒ 40 + 2m = 100 + m
   ⇒ m = 60 ml

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289. An ore contains 25% of an alloy that has 90% iron. Other than this, in the remaining 75% of the ore, there is no iron. To obtain 60 kg of pure iron, the quantity of the ore needed (in kgs) is approximately :

1. 1. 250.57

   
   
   

   2. 266.67

   
   
   

   3. 275.23

   
   
   

   4. 300

   
   
   

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1. View Hint View Answer Discuss in Forum

   In 4 kg of ore iron = 0.9 kg.
   

   ∴ Quantity of ore for 60 kg of iron =	60 × 4
   	0.9

   Correct Option: B

   In 4 kg of ore iron = 0.9 kg.
   

   ∴ Quantity of ore for 60 kg of iron =	60 × 4	= 266.67 kg
   	0.9

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290. A litre of pure alcohol is added to 6 litres of 30% alcohol solution. The percentage of water in the solution is

1. 1. 50%

   
   
   

   2. 65%

   
   
   

   3. 60%

   
   
   

   4. 40%

   
   
   

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1. View Hint View Answer Discuss in Forum

   In 30% alcohol solution,
   

   Alcohol =	30	× 6 = 1.8 litres
   	100

   
   Water = 4.2 litres
   On mixing 1 litre of pure alcohol,
   

   Correct Option: C

   In 30% alcohol solution,
   

   Alcohol =	30	× 6 = 1.8 litres
   	100

   
   Water = 4.2 litres
   On mixing 1 litre of pure alcohol,
   

   Percentage of water =	4.2	× 100 = 60%
   	7

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