Question: 36 -

A 144 litres of mixture contains milk and water in the ratio 5 : 7. How much milk need to be added to this mixture so that the new ratio is 23 : 21 respectively?

Options:

32 litres

40 litres

36 litres

28 litres

Answer:

32 litres

Solution:

144 == 5:7
60 : 84
Now == 21 = 84
23 = 92
92-60 = 32

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Question: 37 -

In a 100 litre mixture of milk and water, the % of water is only 20%. The milkman gave 25 litres of this mixture to a customer and then added 25 litres of water to the remaining mixture. What is the % of milk in the final mixture?

Options:

68%

57%

53%

60%

Answer:

60%

Solution:

80: 20 == 4:1
25 == 20:5
60 : 15
60 : 15+25 == 60:40
60%

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Question: 38 -

A can contains 50 litres of milk. 10 litres of this milk is taken out and replaced with water. This process is repeated twice. Find the amount of remaining milk in the mixture? 

Options:

127/3 litres

87litres

128/5litres

26 2/3 litres

Answer:

128/5litres

Solution:

Remaining milk = 50 [1 – (10/50)]3 = 128/5

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Question: 39 -

How many kgs of rice of variety-1 costing Rs.42/kg should a shopkeeper mix with 25 kgs of rice of variety-2 costing Rs.24 per kg so that he makes a profit of 25% on selling the mixture at Rs.40/kg?

Options:

20

25

15

30

Answer:

20

Solution:

25% profit by selling the mixture at Rs.40/kg, his cost per kg of the mixture = Rs.32/kg.
(x×42)+(25×24)=32(x+25)
42x+600=32x+800
10x=200
x=20kgs.
Shortcut:
125 = 40
100 = 32
42……………….24
………32…………..
8…………………….10
10 = 25
8 = 20

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Question: 40 -

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

Options:

1/4

5 1/9

4 1/7

1/8

Answer:

1/8

Solution:

In the first alloy,
2:3:1     =6*2
5:4:3 =12
Multiply 2 to make it equal,
4:6:2
5:4:3
Adding all,
4:11:6:3=24
3/24=1/8

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