Answer:
Johnny's result will be identical compared with rest of class
Step-by-step explanation:
- Density is the ratio of mass to volume
- If mass increases/decreases then volume also increases/decreases proportionally. Hence density remains constant
- Johnny ate half of it's brownie. So mass of brownie becomes half of it's original mass. Volume of brownie also becomes half of it's original mass
- Density of brownie =

- So Johnny's result will be identical compared with rest of class.