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1. 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? | |

A. 29.16 litres | B. 28 litres |

C. 28.2 litres | D. 26 litres |

Answer: Option A

Explanation:

Suppose a container contains $x$ units of a liquid from which $y$ units are taken out and replaced by water. After $n$ operations, quantity of pure liquid

$=x\left(1-\dfrac{y}{x}\right)^n$ units.

$=x\left(1-\dfrac{y}{x}\right)^n$ units.

milk contained by the container now

$=40\left(1-\dfrac{4}{40}\right)^3\\= 40\left(1-\dfrac{1}{10}\right)^3 \\=40×\dfrac{9}{10}×\dfrac{9}{10}×\dfrac{9}{10}\\= \dfrac{4×9×9×9}{100}\\= 29.16$

prince

2014-12-16 18:28:30

they have taken 4 ltr of water each time that means totally 12 ltr right ?

40-12 =28

how come that is 29.16

plz explain

40-12 =28

how come that is 29.16

plz explain

Khutsie Nfila

2020-03-03 16:44:46

But can't it be divide lets say 40/12 which is going to be the answer so plz explain i did my working.

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Vaijayanti

2014-12-20 19:53:25

each time 4 L milk is taken and replaced with water.

Initially when 4 litre of milk is taken and replaced with water, the solution will have 36 litre of milk and 4 litre of water.

Next time when 4 litre is taken from this solution, milk component removed = 4*36/40 = 3.6

after this process, the solution will contain 32.4 litre of milk and 7.6 litre of water

next time, 4*32.4/40= 3.24 litre of milk gets removed.

Total quantity of milk becomes 32.4 - 3.24 = 29.16

Initially when 4 litre of milk is taken and replaced with water, the solution will have 36 litre of milk and 4 litre of water.

Next time when 4 litre is taken from this solution, milk component removed = 4*36/40 = 3.6

after this process, the solution will contain 32.4 litre of milk and 7.6 litre of water

next time, 4*32.4/40= 3.24 litre of milk gets removed.

Total quantity of milk becomes 32.4 - 3.24 = 29.16

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Harini

2014-01-16 06:59:15

RAKESH:

From 40 liters 4 liters of milk is replaced by water three times.

then,

practically 40-(4*3) = 40-12 = 28.

.

. . ans is 28liters.

Jay

2014-01-19 19:35:41

water and milk are 4 litre and 36 litre respectively (ratio is 1:9)

quantity of water removed = 4 * (1/10) = 2/5

quantity of milk removed = 4 * (9/10) = 18/5

New quantity of Milk=36-18/5=162/5

New quantity of Water = 4-2/5=18/5

After addition of water,milk is same quantity (162/5)

New quantity of water = 18/5 + 4 =38/5

(ie, now ratio of water and milk is 38 : 162 = 19 : 81)

quantity of milk removed = 4 * (81/100) = 81/25

New quantity of Milk=162/5-81/25=29.16 litre

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sandeep

2013-11-19 12:26:54

bcz 40/10=4

thts why eqution is (4*9*9*9)/100

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Raj

2013-11-16 11:31:06

40/10 is also done in the same step and hence it is 4. Remaining is 10*10 which is 100.

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