Cost of $1$ dozen of bananas is Rs.$42$. What is the cost of $3\dfrac{1}{2}$ dozen of bananas?

Hint: Use unitary method i.e. find the cost x units of items by simply multiplying x with the cost of 1 unit of that item.

Using unitary method,
$1$dozen of bananas are of Rs$ = 42$
So, $3\dfrac{1}{2}$ dozen of bananas are of Rs\[ = 42 \times 3\dfrac{1}{2}\]
                        \[\begin{gathered}
   = 42 \times \dfrac{7}{2} \\
   = 21 \times 7 \\
   = 147 \\
\end{gathered} \]
Hence, Cost of$3\dfrac{1}{2}$dozen of bananas is 147 Rs.

Note: In unitary method, we need to find info of a single unit. Then the multiplication will give us the answer. That’s what we have done in this question. We had given the cost of one dozen bananas and we just multiplied it with$3\dfrac{1}{2}$.