The formula to solve this problem is:
c = b + gmc=b+gm
Where:
cc is the current weight - 16 pounds for this problem.
bb is the weight at birth or start of a period of time - 7 pounds for this problem.
gg is the weight change per month - 1.5 pounds for this problem.
mm is the age or number in months - what we are solving for in this problem.
Substituting and solving for mm gives:
16 = 7 + 1.5m16=7+1.5m
-color(red)(7) + 16 = -color(red)(7) + 7 + 1.5m−7+16=−7+7+1.5m
9 = 0 + 1.5m9=0+1.5m
9 = 1.5m9=1.5m
9/color(red)(1.5) = (1.5m)/color(red)(1.5)91.5=1.5m1.5
6 = (color(red)(cancel(color(black)(1.5)))m)/cancel(color(red)(1.5))
6 = m
m = 6
It will take an average female infant an average of color(red)(6) months to go from an average birth weight of 7 pounds to 16 pounds if she gains an average of 1.5 pounds per month.
