Given that amount of tomatoes bought by Amy = 0.4 kilogram
Total amount paide for 0.4 kilogram of tomatoes = $4.00
Now we have to find the cost in dollars per kilogram of tomatoes. That means find what is cost of 1 kilogram of the tomatoes.
We can setup ratio of tomatoes and price to easily find the answer.
![(Cost \; of ; tomato)/(weight \;of \; tomato)=(Cost \; of \; 1kg \; tomato)/(1)=(4.00)/(0.4 )](https://img.qammunity.org/2019/formulas/mathematics/high-school/iseelw60qdffj3cndjbaxgizg8l7tap173.png)
![(Cost \; of \; 1kg \; tomato)/(1)=(4.00)/(0.4 )](https://img.qammunity.org/2019/formulas/mathematics/high-school/5zu1swmp5minpjxfj8mc5hsgribw447vtd.png)
![Cost \; of \; 1kg \; tomato=10](https://img.qammunity.org/2019/formulas/mathematics/high-school/4kjugzj8hgiisackln9mt34sgpxpohjjdt.png)
Hence final answer is $10.