Final answer:
The baby would grow approximately 0.15 cm in 3 hours.
Step-by-step explanation:
To determine the speed of the baby's growth in 3 hours, we need to convert the given measurements into the same unit, which is centimeters per hour. Given that 1 day = 24 hours, and the baby grows 1.2 cm per month during the second six months, we can calculate the growth rate by dividing 1.2 cm by the number of days in a month and then multiplying by 24 to get the growth rate in centimeters per hour. Using this approach, the baby grows at a rate of approximately 0.05 cm/hour during the second six months. Therefore, the baby would grow approximately 0.15 cm in 3 hours.