Percentages Part 8

Milk and water concept

Problem 1: A mixture of 40 lit of milk and water contains 10% water. How much water should be added so water may 20% in the mixture

Solution: Quantity of mixture  = 40 lit.

Percentage of water = 10%

The quantity of water = \frac{40\times 10}{100}=4 lit

The quantity of milk = 40-4=36

How much water should be added so water maybe 20% in the new mixture

\frac{4+x}{36}=\frac{20}{80}

x=5

Shortcut :

Water                      Milk                     Water                      Milk

10             :                90          \rightarrow             1               :               9

20             :                80         \rightarrow              1              :                4

To equate the milk multiply (1:9) with 4 and (1:4) with 9

Water                      Milk                                    Water                      Milk

( 1               :               9 )  *4          \rightarrow                      4               :              36

( 1               :               4 )  *9          \rightarrow                       9              :              36

4-9=5

\rightarrow  40

40 \rightarrow  ?     (36+4=40)

\frac{5\times 40}{40}=5lit

Problem 2: Fresh fruit contains 68% water and dry fruit contains 20% water. How many kgs of dry fruits can be made from 75kg of fresh fruit?

Solution :

Water                 pulp                               Water                 pulp

Fresh              68%          :         32%            \rightarrow                17           :             8

Dry                    20%          :        80%            \rightarrow                  2          :               8

17+8=25             2+8=10

25%  \rightarrow  75

10%  \rightarrow  ?

\frac{10\times 75}{25}=30

Problem 3: A solution of salt water contains 20% salt by weight. If 20lit of water is evaporated from the solution, the solution contains 25% of salt. What is the original quantity of solution?

Solution:

Salt                     Water                   Salt                     Water

20%       :             80%        \rightarrow             1           :               4

25%      :              75%        \rightarrow              1           :              3

1+4=5          1+3=4

5-4=1

\rightarrow  20lit

\rightarrow  ?

\frac{5\times 20}{1}=100

 

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