One hundred monkeys have \[100\] apples to divide. Each adult gets three apples while three children share one. The number of adult monkeys is $ ........... $ .
 $ \left( a \right){\text{ 20}} $
 $ \left( b \right){\text{ 25}} $
 $ \left( c \right){\text{ 30}} $
 $ \left( d \right){\text{ 33}} $

Hint: For solving this question we will use the unitary method for it. Since, from the question we can see that the ratio of adults and children is given as $ 3:1 $ , which means in total we have $ 4 $ . And from this, we will calculate the number of apples for adults. And then applying the unitary method we will have the number of adult monkeys.

Complete step-by-step answer:
So first of all we will see the values given to us. Since it is given that the number of apples is $ 100 $ .
And also it is given that $ 1 $ adults get $ 3 $ apples and the $ 3 $ children get $ 1 $ apples.
So from this, the ratio of adult and children will be as $ 3:1 $ , which means in total we have $ 4 $
So, the number of apples for an adult will be given by
 $ \Rightarrow \dfrac{3}{4} \times 100 $
And on solving the above fraction, we get
 $ \Rightarrow 75 $
Since $ 3 $ apple is for $ 1 $ adults.
Therefore, $ 75 $ apple will be for $ \dfrac{{75}}{3} $
And on solving the fraction by dividing it, we get
 $ \Rightarrow 25 $
Hence, the number of the adult monkey will be $ 25 $
Therefore, the option $ \left( b \right) $ is correct.
So, the correct answer is “Option b”.

Note: This type of question can be solved easily if we read the statement of the question carefully and we understand it is based on applications of fractions. A fraction represents a part of a whole or, more generally, any number of equal parts.