Question

At a camp, there is sufficient food to last for $ 15 $ students for $ 30 $ days. After $ 4 $ days, $ 2 $ students left the camp. How much longer will the food last?

Answer 1

Hint: Try to solve this problem with basic mathematics calculations that are unitary methods. Get the food amount taken by each student on a single day and the total food amount that we have. After $ 4 $ days, $ 2 $ students leave the camp, then calculate the food consumption by remaining students that are present in the camp.

Complete Step By Step Answer:
Given :
Number of students present on first day $ = $ $ 15 $ students
Food amounts last for $ 30 $ days for $ 15 $ students.
Let us assume that one student will consume 1 food packet per day.
Therefore, Number of packets that we have with us $ = $ $ (15 \times 30) $ $ {\text{packets}} $ $ = $ $ 450{\text{ packets}} $
Number of packets consumed per day $ = $ $ \dfrac{{450}}{{30}}{\text{ packets}} $ $ = $ $ 15{\text{ packets}} $
Now, according to question number of packets consumed for the first 4 days $ = $ $ (15 \times 4){\text{ packets}} = 60{\text{ packets}} $
Remaining number of packets that we have $ = $ $ (450 - 60) $ $ = $ $ 390{\text{ packets}} $
Now, to calculate number of days,
Number of students present after 4th day $ = $ $ 13{\text{ students}} $
Number of packets that we have $ = $ $ 390{\text{ packets}} $
Number of days for which $ 390{\text{ packets}} $ will last $ = $ $ \dfrac{{390}}{{13}}{\text{ days = 30 days}} $
Therefore, the total number of days the given amount of food will last $ = $ $ (30 + 4){\text{ = 34 days}} $ .

Note:
The unitary method is a technique for solving a problem by first finding the value of a single unit, and then finding the necessary value by multiplying the single unit value. In essence, this method is used to find the value of a unit from the value of a multiple, and hence the value of a multiple.