Answer:
62 inches
Step-by-step explanation:
Let x be the height ( in inches ) of Ivan,
∵ Marcia is 5 inches shorter than Ivan,
height of Marcia = x - 5,
Marcia is twice as tall as Sally-Jo,
height of sally-jo = [tex]\frac{x-5}{2}[/tex]
Mom is 2 inches taller than Ivan.
⇒ height of mom = x + 2,
Mom is 3 inches shorter than Dad,
height of dad = x + 2 + 3 = x + 5,
So, mean height of family is,
[tex]\frac{x+x-5+\frac{x-5}{2}+x+2+x+5}{5}[/tex]
[tex]=\frac{2x+2x-10+x-5+2x+4+2x+10}{10}[/tex]
[tex]=\frac{9x-1}{10}[/tex]
According to the question,
x + 5 = 74 ( 1 ft = 12 in )
x = 69
Hence, mean height of the family = [tex]\frac{9\times 69-1}{10}[/tex]
[tex]=\frac{620}{10}[/tex]
= 62 inches
