Final answer:
From age 6-12 months, infants generally gain about 0.45 kg (1 lb) per month and grow about 2.5 cm (1.0 in.) per month during the first six months, and about 1.2 cm (0.5 in.) per month during the second six months.
Step-by-step explanation:
The normal weight gain for infants from age 6-12 months is about 0.45 kg (1 lb) per month. At this rate, an infant generally doubles its birth weight by six months and triples its birth weight by 12 months. In terms of length, infants grow about 2.5 cm (1.0 in.) per month during the first six months and about 1.2 cm (0.5 in.) per month during the second six months. By the end of the first year, an infant may close to double its birth length.