Sail E0 Webinar

Quantitative Aptitude

ALLIGATION MCQs

Total Questions : 48 | Page 4 of 5 pages
Question 31.

A vessel is filled with liquid, 3 parts of which are water and 5 parts syrup. How much of the mixture must be drawn off and replaced with water so that the mixture may be half water and half syrup?

  1.    \(\frac{1}{3}\)
  2.    \(\frac{1}{4}\)
  3.    \(\frac{1}{5}\)
  4.    \(\frac{1}{7}\)
 Discuss Question
Answer: Option C. -> \(\frac{1}{5}\)

Suppose the vessel initially contains 8 litres of liquid.


Let x litres of this liquid be replaced with water.


Quantity of water in new mixture = \(\left(3-\frac{3x}{8}+x\right) liters\)


Quantity of syrup in new mixture = \(\left(5-\frac{5x}{8}\right) liters\)


So,  \(\left(3-\frac{3x}{8}+x\right)=\left(5-\frac{5x}{8}\right)\)


5x + 24 = 40 - 5x


 10x = 16


x =  \(\frac{8}{5}\)


So, part of the mixture replaced = \(\left(\frac{8}{5}\times\frac{1}{8}\right)=\frac{1}{5}\)

Question 32.

Tea worth Rs. 126 per kg and Rs. 135 per kg are mixed with a third variety in the ratio 1 : 1 : 2. If the mixture is worth Rs. 153 per kg, the price of the third variety per kg will be:

  1.    Rs. 169.50
  2.    Rs. 170
  3.    Rs. 175.50
  4.    Rs. 180
 Discuss Question
Answer: Option C. -> Rs. 175.50

Since first and second varieties are mixed in equal proportions.


So, their average price = Rs.     = Rs.130.50


So, the mixture is formed by mixing two varieties, one at Rs. 130.50 per kg and the other at say, Rs. x per kg in the ratio 2 : 2, i.e., 1 : 1. We have to find x.


By the rule of alligation, we have:


 


Cost of 1 kg of 1st kindCost of 1 kg tea of 2nd kind
Rs. 130.50
Mean Price
Rs. 153
Rs. x
(x - 153)
22.50

 


\(\frac{x-153}{22.50}=1\) 


x - 153 = 22.50


Tea Worth Rs. 126 Per Kg And Rs. 135 Per Kg Are Mixed With A... x = 175.50

Question 33.

A can contains a mixture of two liquids A and B is the ratio 7 : 5. When 9 litres of mixture are drawn off and the can is filled with B, the ratio of A and B becomes 7 : 9. How many litres of liquid A was contained by the can initially?

  1.    10
  2.    20
  3.    21
  4.    25
 Discuss Question
Answer: Option C. -> 21

Suppose the can initially contains 7x and 5x of mixtures A and B respectively


Quantity of A in mixture left = \(\left(7x-\frac{7}{12}\times9\right) liters=\left(7x-\frac{21}{4}\right) liters\)


Quantity of B in mixture left = \(\left(5-\frac{5}{12}\times9\right) liters=\left(5x-\frac{15}{4}\right) liters\)


So,  \(\frac{\left(7x-\frac{21}{4}\right)}{\left(5x-\frac{15}{4}\right)+9}=\frac{7}{9}\)


\(\frac{28x-21}{20x+21}=\frac{7}{9}\)


 252x - 189 = 140x + 147


 112x = 336


 x = 3.


So, the can contained 21 litres of A.

Question 34.

A milk vendor has 2 cans of milk. The first contains 25% water and the rest milk. The second contains 50% water. How much milk should he mix from each of the containers so as to get 12 litres of milk such that the ratio of water to milk is 3 : 5?

  1.    4 litres, 8 litres
  2.    6 litres, 6 litres
  3.    5 litres, 7 litres
  4.    7 litres, 5 litres
 Discuss Question
Answer: Option B. -> 6 litres, 6 litres

Let the cost of 1 litre milk be Re. 1


Milk in 1 litre mix. in 1st can = \(\frac{3}{4}\)  litre, C.P. of 1 litre mix. in 1st can Re   \(\frac{3}{4}\)


Milk in 1 litre mix. in 2nd can = \(\frac{1}{2}\) litre, C.P. of 1 litre mix. in 2nd can Re   \(\frac{1}{2}\)


Milk in 1 litre of final mix.= \(\frac{5}{8}\)    litre, Mean price = Re    \(\frac{5}{8}\)


By the rule of alligation, we have:


C.P. of 1 litre mixture in 1st can  =  \(\frac{3}{4}\)


C.P. of mixture in 2nd can  =  \(\frac{1}{2}\)


Main price  =  \(\frac{5}{8}\)


So, Ratio of two mixtures = \(\frac{1}{8}:\frac{1}{8}=1:1\)


So, quantity of mixture taken from each can = \(\left(\frac{1}{2}\times12\right)= 6 litres\)

Question 35.

In what ratio must a grocer mix two varieties of pulses costing Rs. 15 and Rs. 20 per kg respectively so as to get a mixture worth Rs. 16.50 kg?

  1.    3 : 7
  2.    5 : 7
  3.    7 : 3
  4.    7 : 5
 Discuss Question
Answer: Option C. -> 7 : 3

By the rule of alligation:


Cost of 1 kg pulses of 1st kind = Rs.15


Cost of 1 kg pulses of 2nd kind Rs.20


Main price = Rs. 16.50


So,Required rate = 3.50 : 1.50 = 7 : 3.

Question 36.

In what ratio must a grocer mix two varieties of pulses costing Rs. 15 and Rs. 20 per kg respectively so as to get a mixture worth Rs. 16.50 kg?

  1.    3 : 7
  2.    5 : 7
  3.    7 : 3
  4.    7 : 5
 Discuss Question
Answer: Option C. -> 7 : 3

By the rule of alligation:


Cost of 1 kg pulses of 1st kind = Rs.15


Cost of 1 kg pulses of 2nd kind Rs.20


Main price = Rs. 16.50


So,Required rate = 3.50 : 1.50 = 7 : 3.

Question 37.

A dishonest milkman professes to sell his milk at cost price but he mixes it with water and thereby gains 25%. The percentage of water in the mixture is:


 

  1.    4%
  2.    \(6\frac{1}{4}\)%
  3.    20%
  4.    25%
 Discuss Question
Answer: Option C. -> 20%

Let C.P. of 1 litre milk be Re. 1


Then, S.P. of 1 litre of mixture = Re. 1, Gain = 25%.


C.P. of 1 litre mixture = Re. \(\left(\frac{100}{125}\times1\right)=\frac{4}{5}\)


By the rule of alligation, we have:


C.P. of 1 litre of milk = Rs.1


C.P. of 1 litre of water = 0


So, Ratio of milk to water = \(\frac{4}{5}:\frac{1}{5}=4:1.\)


Hence, percentage of water in the mixture =  \(\left(\frac{1}{5}\times100\right)\)  % = 20%


 

Question 38.

How many kilogram of sugar costing Rs. 9 per kg must be mixed with 27 kg of sugar costing Rs. 7 per kg so that there may be a gain of 10% by selling the mixture at Rs. 9.24 per kg?

  1.    36 kg
  2.    42 kg
  3.    54 kg
  4.    63 kg
 Discuss Question
Answer: Option D. -> 63 kg

S.P. of 1 kg of mixture = Rs. 9.24, Gain 10%.


So, C.P. of 1 kg of mixture = Rs. \(\left(\frac{100}{110}\times9.24\right)=Rs. 8.40\)


By the rule of allilation, we have:


C.P. of 1 kg sugar of 1st kind = Rs.9


Cost of 1 kg sugar of 2nd kind = Rs.7


Main Price = Rs. 8.40


So, Ratio of quantities of 1st and 2nd kind = 14 : 6 = 7 : 3.


Let x kg of sugar of 1st be mixed with 27 kg of 2nd kind.


Then, 7 : 3 = x : 27


x= \(\left(\frac{7\times27}{3}\right)= 63 kg.\)

Question 39.

A container contains 40 litres of milk. From this container 4 litres of milk was taken out and replaced by water. This process was repeated further two times. How much milk is now contained by the container?

  1.    26.34 litres
  2.    27.36 litres
  3.    28 litres
  4.    29.16 litres
 Discuss Question
Answer: Option D. -> 29.16 litres

Amount of milk left after 3 operations = \(\left[40\left(1-\frac{4}{140}\right)^{3}\right]litres\)


\(\left(40\times\frac{9}{10}\times\frac{9}{10}\times\frac{9}{10}\right) =29.16 litres.\)

Question 40.

A jar full of whisky contains 40% alcohol. A part of this whisky is replaced by another containing 19% alcohol and now the percentage of alcohol was found to be 26%. The quantity of whisky replaced is:

  1.    \(\frac{1}{3}\)
  2.    \(\frac{2}{3}\)
  3.    \(\frac{2}{5}\)
  4.    \(\frac{3}{5}\)
 Discuss Question
Answer: Option B. -> \(\frac{2}{3}\)

By the rule of alligation, we have:


Strength of first jar = 40%


Strength of 2nd jar = 19%


Main Strength = 26%


So, ratio of 1st and 2nd quantities = 7 : 14 = 1 : 2


So, Required quantity replaced = \(\frac{2}{3}\)

To solve this problem, let us first define some variables.
Lets say,
Q = Quantity of whisky in the jar
%A = Percentage of alcohol in the jar
%B = Percentage of alcohol in the whisky replaced

We are given the following information:
Q = 1
%A = 40 %
%B = 19 %

Now, the task is to find the quantity of whisky replaced.

Now, using the formula for finding the percentage, we can write:

%A = (Quantity of whisky with 40% alcohol/Total Quantity of whisky)*100

%B = (Quantity of whisky with 19% alcohol/Total Quantity of whisky)*100

From the given information, we can write:

40% = (Q/Q)*100
19% = (Q2/Q)*100

Where Q2 is the quantity of whisky replaced with 19% alcohol.

Now, we need to find the value of Q2.

To do this, let us rearrange the equation to get:
Q2 = (19/40)*Q

Now, we need to find the value of Q.

To do this, let us rearrange the equation to get:
Q = (40/19)*Q2

Substituting the value of Q2 in the equation, we get:
Q = (40/19)*(19/40)*Q

Simplifying the equation, we get:
Q = (40/19)*Q

Dividing both the sides by Q, we get:
(40/19)*Q/Q = 1

Simplifying the equation, we get:
40/19 = 1

Now, we need to find the value of Q2.

Substituting the value of Q in the equation, we get:
Q2 = (19/40)*(40/19)*Q

Simplifying the equation, we get:
Q2 = Q

Therefore, the quantity of whisky replaced is equal to the total quantity of whisky in the jar.

Hence, the answer is Option B 2/3

If you think the solution is wrong then please provide your own solution below in the comments section .

Latest Videos

Latest Test Papers