Question

If 15 dozen eggs cost \[Rs\text{ }720\], what will be the cost of \[\text{5 score }eggs\]?\[\text{ }\left[ 1\text{ score = 20 units} \right]\].

Answer 1

Hint: The cost of 15 dozen eggs is Rs 720, then we can find the cost of 1 egg by using a unitary method and the cost of 5 score eggs can be calculated by multiplying it to the cost of the unit egg.
\[\text{Cost of 1 }egg\text{ = }\dfrac{\text{Cost of total eggs}}{total\text{ number of eggs}}\]

Complete step-by-step answer:
First step will be to calculate the cost of the unit egg.
The unit egg cost is multiplied by 5 score that is 100, then
The cost of 5 score eggs is obtained.
The cost of eggs can be obtained as,
\[\begin{align}
  & \text{cost of }15\text{ }dozen\text{ }eggs\text{ = }Rs\text{ }720 \\
 & \text{cost of }15\cdot 12\text{ }eggs\text{ = }Rs\text{ }720 \\
 & \text{cost of 300 }eggs\text{ = }Rs\text{ }720 \\
 & \text{cost of 1 }egg\text{ = Rs }\dfrac{720}{300} \\
 & \text{cost of 1 }egg\text{ = }Rs\text{ 2}\text{.40} \\
 & \text{cost of 5 score }eggs\text{ = }Rs\text{ 2}\text{.40}\cdot \left( 5\cdot 20 \right)\text{ }\left[ \because 1\text{ score = 20 units} \right] \\
 & \text{cost of 5 score }eggs\text{ = }Rs\text{ 2}\text{.40}\cdot 100 \\
 & \text{cost of 5 score }eggs\text{ = }Rs\text{ 240} \\
\end{align}\]
Thus, the cost of 5 score eggs = Rs 240.

Note: The problem is solved by the method called unitary method.
 The unitary method is used to solve the problem by finding the value of a single unit, then finding the necessary value by multiplying the single unit value.