Answer:
Carmen's water bottle holds 1 8/10 liters of water, which can be written as 18/10 liters or 1.8 liters.
Jorge's water bottle holds 2 2/5 liters of water, which can be written as 22/5 liters or 4.4 liters.
Jorge's estimate of his water bottle holding about 1/2 liter more water than Carmen's is reasonable because:
4.4 liters (Jorge's bottle) - 1.8 liters (Carmen's bottle) = 2.6 liters
2.6 liters is close to the estimate of 1/2 liter, so Jorge's estimate is reasonable.