in hostel of 40 students there is food for 30 days if 20 more students join the hostel how long will the food last

The food will last for 20 days

Step-by-step explanation:

The equation of the inverse proportional is xy = k, where k is the constant of variation

∵ In a hostel of 40 students, there is food for 30 days

→ That means the food is the constant k and the number of days y

   varies inversely with the number of students x

∴ x = 40 and y = 30

∵ xy = k

∴ 40 × 30 = k

∴ 1200 = k

∴ The equation of the inverse proportional is xy = 1200

∵ 20 more students join the hostel

→ That means the number of students increased by 20

∴ The number of students in the hostel = 40 + 20

∴ The number of students in the hostel = 60

→ By using the equation above

∵ 60 × y = 1200

∴ 60y = 1200

→ Divide both sides by 60

∴ y = 20

∴ The food will last for 20 days

to determine the unit cost your would divide the total cost by the number sold.

7 bagels for $4.41       $4.41/7 = $.63 each at fresh side

5 bagels for $3.60         $3.60/5 = $.72 each at value mart