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

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.