At RSM summer camp 100 students had enough food for a 30-days stay. After 2 days 40 new students joined the camp. After that 2 weeks passed and half of the students left the camp. How many additional days of food need to be ordered?

"no additional days of food need to be ordered."

Step-by-step explanation:

Suppose initial quantity of food is x units

Assuming each student eats 1 unit of food per day,

x = 30 * 100 = 3000 units of food

In 2 days, food eaten:

100 * 1 * 2 = 200 units

So food left after 2 days is 3000 - 200 = 2800 units

Now, there are 140 students. They stay 2 weeks (14 days) - 2 = 12 more days

So food eaten in 12 days:

140 * 1 * 12 = 1680 units

THus, after total 14 days gone, the amount of food left is:

2800 - 1680 = 1120 units

Half students left, so there are 70 students left for the last 16 days. How much food would they need?

70 * 1 * 16 = 1120 units

And there are exactly 1120 units left. So, no additional days of food need to be ordered.