Cup : Coffee :: Bowl : Soup

Because Coffee goes into a Cup and Soup goes into a Bowl where Food is a general thing and Mug is an other utensil. 

So, Cup is to Coffee as Bowl is to Soup.

Here the given series 1, 6,  ?, 15, 45, 66, 91 follows a

Pattern in the series is, +5, +9, +13,...,.. +21, +25

So +4 is getting increased at every term addition.

Missing Number in the series will be 15+(9+4) = 15 + 13 = 28.

The given equation is in Mixed fraction.

Now to solve this type of fractions,

$$\begin{gathered} 413 + 215 + 414 =? \\ ? = 4 + 2 + 4 + 13 + 15 + 14 \\ ? = 10 + 4760 \\ ? = 104760 \\ \end{gathered}$$

Hydrogen is the common element to all Acids. But every element which contains Hydrogen is not an Acid. Most of the acids also contain Oxygen.

It is Blackboard or Chalkboard which is Black when clean, and as you write on it with white chalk it becomes dirty in White color.

Arithmetic Series ::

An Arithmetic Series is a series of numbers in which each term increases by a constant amount.

How to find the sum of the Arithmetic Sequence or Series for the given Series ::

When the series contains a large amount of numbers, its impractical to add manually. You can quickly find the sum of any arithmetic sequence by multiplying the average of the first and last term by the number of terms in the sequence.

That is given by Sn = n(a1 + an)2 Where n = number of terms, a1 = first term, an = last term

Here Last term is given by an = a1 + n-1d where d = common difference

Now given Arithmetic Series is 

2, 5, 8, 11,...

Here a1 = 2,  d = 3, n = 36 

Now, $$\begin{gathered} an= a1 + n - 1d \\ a36= 2 + 36 - 13 = 105 + 2 = 107 \end{gathered}$$

Now, Sum to 36 terms is given by

S36 = 36(2 + 107)2 = 36 x 1092 = 39242 = 1962

Therefore, Sum to 36 terms of the series 2, 5, 8, 11,... is 1962.

Customer ratio of Milk and Water is given by

Milk          ::        Water

  6.4                         0

         81 + 38 =6411

 6411                      6410 - 6411

=> Milk : Water = 110 : 11 = 10 : 1

Therefore, the proportionate of Water to Milk for Customer is 1 : 10

Given nuber series is 15, 30, ? , 40, 8, 48 

Here the number series follows a pattern that

15

15 x 2 = 30

30 ÷ 3 = 10

10 x 4 = 40

40 ÷ 5 = 8

8 x 6 = 48

Hence, the missing number in the series is 10.