Final answer:
To calculate the cost of 3kg of onions, divide the total cost for 4kg ($3.40) by 4 to get the cost per kilogram, and then multiply by 3.
Step-by-step explanation:
To determine the cost of 3kg of onions when 4 kg of onions costs $3.40, you first find the cost of 1 kg by dividing the total cost by the number of kilograms. The cost per kilogram is $3.40 divided by 4kg, which is $0.85 per kg. Then, to find the cost of 3kg of these onions, multiply the cost per kilogram by 3kg. So, the cost for 3kg is $0.85 per kg multiplied by 3kg, which equals $2.55.
Or To find the cost of 3kg of onions, we can use the given information that 4kg of onions costs $3.40. We can set up a proportion to solve for the cost of 3kg of onions:
4kg/3.40 = 3kg/x
To solve for x, we can cross multiply:
4kg * x = 3kg * 3.40
x = (3kg * 3.40) / 4kg
Calculating the value, we get x = $2.55
Therefore, the cost of 3kg of these onions is $2.55.