SOLUTION: Could a Tutor Please help me with this word problem..I don't know where to start??? Age-48 yrs Height 5 feet 7 inches The volume of air an adult's lungs can hold decreases

Algebra ->  Linear-equations -> SOLUTION: Could a Tutor Please help me with this word problem..I don't know where to start??? Age-48 yrs Height 5 feet 7 inches The volume of air an adult's lungs can hold decreases      Log On


   

Question 85395: Could a Tutor Please help me with this word problem..I don't know where to start??? Age-48 yrs Height 5 feet 7 inches

The volume of air an adult's lungs can hold decreases with age. The equation:
V = 0.104h – 0.018a – 2.69
gives an estimate of the air volume V (in liters) of a person's lungs for someone of height h inches and age a years.
A. Using your own height and weight in the equation above, calculate your estimated lung volume.
B. Calculate 90% of your lung volume.
C. Solve the equation above for the variable a.
D. Calculate how old you will be when your air volume is 90% of its current value. (Use your current height.)
E. Substitute your current height for h in the original equation, and graph the equation to show how air volume changes as age increases.

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Age-48 yrs Height 5 feet 7 inches
:
The volume of air an adult's lungs can hold decreases with age. The equation:
V = 0.104h – 0.018a – 2.69
gives an estimate of the air volume V (in liters) of a person's lungs for someone of height h inches and age a years.
:
A. Using your own height and weight in the equation above, calculate your estimated lung volume.
(assume you mean height and "age")
:
Change 5'8" to inches: 5*12 = 60 + 7 = 67"
:
Substitute 67 for h and 48 for a
V = .104(67) - .018(48) - 2.69
V = 6.968 - .864 - 2.69
V = 3.414 liters
:
B. Calculate 90% of your lung volume.
.9 * 3.414 = 3.0726 liters
:
C. Solve the equation above for the variable a.
.104h - .018a - 2.69 = V
-.018a = V - .104h + 2.69
+.018a = +.104h - V - 2.69; multiplied equation by -1
a = %28%28.104h+-+V+-+2.69%29%29%2F.018
:
:
D. Calculate how old you will be when your air volume is 90% of its current value. (Use your current height.)
:
Substitute 3.0726 (from B) in the above equation and find a
a = %28%28.104%2867%29+-+3.0726+-+2.69%29%29%2F.018
a = %28%286.968+-+3.0726+-+2.69%29%29%2F.018
a = %28%281.2054%29%29%2F.018
a = 67 yrs
:
E. Substitute your current height for h in the original equation, and graph the equation to show how air volume changes as age increases.
:
Original equation:
V = 0.104h – 0.018a – 2.69
Substitute 67 for h
V = .104(67) - .018a - 2.69
V = 6.968 - 2.69 - .018a
V = 4.278 - .018a
To graph this:
y = 4.278 - .018x
Should look like this:
+graph%28+300%2C+200%2C+-20%2C+100%2C+-1%2C+6%2C+-.018x+%2B+4.278%29+
Volume of air on the y axis, age on the x axis
:
Did this make sense to you??