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Q:

Application of Inverse Proportion

If 20 persons can do a piece of work in 7 days then calculate the number of persons require to complete the work in 28 days

Answer

Number of persons * days = work

20 * 7 = 140 man- days

Now, x * 28 = 140 men- days

=> x =5

Therefore in second case the required number of person is 5.

Second method:

Since work is constant, therefore M1 x D1= M2 x D2

20 x 7 = M2 x 28

=> M2 = 5

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Subject: Time and Work

Q:

Concept of Nehative Work

A tub can be filed in 20 minutes but there is a lekage in it which can empty the full tub in 60 minutes. In how many minutes it can be filled?

Answer

Filling efficiency = 5%

Emptying efficiency = 1.66%

Net efficiency = 5-1.66 = 3.33%

Therefore, Required time to fil the tub =100/3.33= 30 minutes

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Subject: Time and Work

Q:

Relation Between Efficiency and Time

A is twice as good a workman as B and is therefore able to finish a piece of work in 30 days less than B.In how many days they can complee the whole work; working together?

Answer

Ratio of times taken by A and B = 1 : 2.

The time difference is (2 - 1) 1 day while B take 2 days and A takes 1 day.

If difference of time is 1 day, B takes 2 days.

If difference of time is 30 days, B takes 2 x 30 = 60 days.

So, A takes 30 days to do the work.

A's 1 day's work = 1/30

B's 1 day's work = 1/60

(A + B)'s 1 day's work = 1/30 + 1/60 = 1/20

A and B together can do the work in 20 days.

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Subject: Time and Work

Q:

From a container, 6 liters milk was drawn out and was replaced by water. Again 6 liters of mixture was drawn out and was replaced by the water. Thus the quantity of milk and water in the container after these two operations is 9:16. The quantity of mixture is:

A) 15	B) 16
C) 25	D) 31

Answer & Explanation Answer: A) 15

Explanation:

Let quantity of mixture be x liters.

Suppose a container contains x units of liquid from which y units are taken out and replaced by Water. After operations , the quantity of pure liquid = $x {(1 - \frac{y}{x})}^{n}$ units, Where n = no of operations .

So, Quantity of Milk = $x {(1 - \frac{6}{x})}^{2}$

Given that, Milk : Water = 9 : 16

=> Milk : (Milk + Water) = 9 : (9+16)

=> Milk : Mixture = 9 : 25

Therefore, $\frac{x {(1 - \frac{6}{x})}^{2}}{x} = \frac{9}{25}$

=> x = 15 liters

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Filed Under: Alligation or Mixture

Q:

The ratio of petrol and kerosene in the container is 3:2 when 10 liters of the mixture is taken out and is replaced by the kerosene, the ratio become 2:3. Then total quantity of the mixture in the container is:

A) 25	B) 30
C) 45	D) cannot be determined

Answer & Explanation Answer: B) 30

Explanation:

pool : kerosene

3 : 2(initially)

2 : 3(after replacement)

$\frac{R e m a i n i n g Q u a n t i t y}{I n i t i a l Q u a n t i t y} = (1 - \frac{R e p l a c e d Q u a n t i t y}{T o t a l Q u a n t i t y})$

(for petrol) $\frac{2}{3} = (1 - \frac{10}{k})$

=> K = 30

Therefore the total quantity of the mixture in the container is 30 liters.

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Filed Under: Alligation or Mixture

Q:

In a mixture of milk and water, there is only 26% water. After replacing the mixture with 7 liters of pure milk , the percentage of milk in the mixture become 76%. The quantity of mixture is:

A) 65 liters	B) 91 liters
C) 38 liters	D) None of these

Answer & Explanation Answer: B) 91 liters

Explanation:

Milk Water

74% 26% (initially)

76% 24% ( after replacement)

Left amount = Initial amount $(1 - \frac{r e p l a c e d a m o u n t}{t o t a l a m o u n t})$

24 = 26 $(1 - \frac{7}{k})$

=> k = 91

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Filed Under: Alligation or Mixture

Q:

The diluted wine contains only 8 liters of wine and the rest is water. A new mixture whose concentration is 30%, is to be formed by replacing wine. How many liters of mixture shall be replaced with pure wine if there was initially 32 liters of water in the mixture ?

A) 4	B) 5
C) 8	D) None of these

Answer & Explanation Answer: B) 5

Explanation:

Wine Water

8L 32L

1 : 4

20 % 80% (original ratio)

30 % 70% (required ratio)

In ths case, the percentage of water being reduced when the mixture is being replaced with wine.

so the ratio of left quantity to the initial quantity is 7:8

Therefore , $\frac{7}{8} = [1 - \frac{K}{40}]$

=> K = 5 Lit

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Filed Under: Alligation or Mixture
Exam Prep: CAT , Bank Exams
Job Role: Bank PO , Bank Clerk

Q:

A jar was full with honey. A person used to draw out 20% of the honey from the jar and replaced it with sugar solution. He has repeated the same process 4 times and thus there was only 512 gm of honey left in the jar, the rest part of the jar was filled with the sugar solution. The initial amount of honey in the jar was filled with the sugar solution. The initial amount of honey in the jar was:

A) 1.25 kg	B) 1 kg
C) 1.5 kg	D) None of these

Answer & Explanation Answer: A) 1.25 kg

Explanation:

Let the initial amount of honey in the jar was K, then

$512 = K {(1 - \frac{1}{5})}^{4}$ $[∵ 20 % = \frac{20}{100} = \frac{1}{5}]$

or

$512 = K {(\frac{4}{5})}^{4}$

Therefore, K = 1250

Hence initially the honey in the jar= 1.25 kg

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Filed Under: Alligation or Mixture

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