Ray feeds his dog 0.12 kilogram of dry dog food each
day. he wants to buy the smallest bag that has
enough food to feed his dog for one month. should
he buy the bag that has 1.8 kilograms, 2.4 kilograms,
or 4.2 kilograms of dog food?

The smallest bag that has enough food to feed his bag for one month

 = 3.6 kilogram

Step-by-step explanation:

The quantity of dry food Ray feeds his dog = 0.12 kilogram

So the quantity of food he feeds his dog in one month

    = 0.12 × 30              ∵ since 1 month = 30 days

    =  3.6 kilogram

The smallest bag that has enough food to feed his bag for one month

 = 3.6 kilogram