Question

Milk is sold in one litre and two litre cartons. A delicatessen owner orders 120 litres of milk and receives 97 cartons. How many of each type did she receive?

Answer 1

let the number of cartons of one litre be x

let the number of cartons of two litre be y

x+y=97 ..... (I)

x+2y=120 ..... (II)

subtract (I) from (II) we get

y=23

x=74

Answer 2

let the no. of 1 litre carton be X and no. of 2 litre carton she received be Y
now,
X + Y = 97 as shown in question............
also
volume of milk in X cartons = X litre ( 1 litre in each carton)
volume of milk in Y cartons = 2Y litre (2 litre in each carton)
therefore,
X + 2Y = 120
now,
X + Y + Y = 120
97 + Y = 120
Y = 23
putting this value of Y in equation ( X + Y = 97 )
X + 23 = 97
X = 74
therefore, she received 74 one litre cartons and 23 two litre cartons.