The polynomial 0.041h-0.018a-2.69 can be used to estimate the lung capacity, in liters, of a female with height h, in cm, and age a, in years. Find the lung capacity of a 40 yr old woman who is 180 centimeters tall. Round to nearest hundredth.

Question

The polynomial 0.041h-0.018a-2.69 can be used to estimate the lung capacity, in liters, of a female with height h, in cm, and age a, in years.  Find the lung capacity of a 40 yr old woman who is 180 centimeters tall.  Round to nearest hundredth.

jim_thompson5910 · Answer

Start with 0.041h-0.018a-2.69 and replace h with the given height 180 and 'a' with the given age 40 to get 



0.041h-0.018a-2.69


0.041(180)-0.018(40)-2.69



Now evaluate and simplify


0.041(180)-0.018(40)-2.69


7.38-0.72-2.69


3.97


So the lung capacity is 3.97 liters.

anonymous · Answer

Thanks!  I got about half way through that (figuring it out) and then I got confused.

jim_thompson5910 · Answer

confused at which part?

anonymous · Answer

I replaced the height and the age (h and a) with 180 and 40...then after that my brain went blank.  LOL

jim_thompson5910 · Answer

ah

jim_thompson5910 · Answer

well whenever you have something like 2x, it means (literally) 2 times x

So if you replace x with some number (say 15), then 2x = 2(15)  = 30


since 2 times 15 equals 30

anonymous · Answer

Right.  If I had a lot of time to sit and ponder it, I can usually figure out the answer, but when I am crunched for time, I get flustered.  Thanks...