Population Problem: A = 65 + 1.7t and B = 26 + 4.1t

[jnice]

If A= 65+1.7t and B= 26+4.1t represent the population (in millions) of two countries, A and B, then in what year will
A) The population of country A equal that of country B?
B) Country A have 30 million more inhabitants than B?
C) Country A have twice as many inhabitants as B?

OK, so I got the answer for part A by setting the two equations equal to each other and solving (that was the easy part) but I am totaling confused on how to set-up the equations for B and C?

For part B- do I set-up the equation like this:

65+1.7t+30000000=26+4.1t

And part C like this:

65+(1.7x2t)=26+4.1t

Or is this something I cannot solve algebraically and I have to use my graphing calulator for?
It seems to me that I need more info to solve these but maybe I am missing something.

Thanks!

 

[Loren]

Re: Population Problem

You are on the right track. But two things come to mind. First---the problem states "in millions" so you don't add or subtract 30,000,000. You use 30.

We are given two equations >>> A= 65+1.7t and B= 26+4.1t.
For the second question it says A is 30 more than B. Therefore we can say A=B+30. If you put B+30 in place of the A in the first given equation, you will then have two equations in two unknowns. Solve for t or B and go from there.

 

[jnice]

Re: Population Problem

Ah ha! Good call on that 30 million! That was really driving me crazy because all the answers I was getting were so large :lol:

OK so just to make sure I understand

For part b...

65 + 1.7t = 26 (+ 30) + 4.1t

For part c...

65 + 1.7t = 2(26) + 4.1t

And than I solve both answers for t and the answers are in the form t= initial year (not given in the question) + the values of t?