<prompt> Bih length doubles by what age?1 year2 years3 years4 years  <response>: Bih length doubles by 4- 4 12 yrs of age Age Bih 1 year 2 year 4 year 12 year Height 50 cm 75 cm 90 cm 100 cm 150 cm Length of child increases by 50 in 1st year. 