Expert: Richard J. Raridon - 5/4/2009

Question
8. At the grocery mart, a 575g can of green beans cost $0.39. How much will an 810 g can of green beans cost?

14. If z is inversely proportional to r, and z = 32 when r = 1.5, find r when z = 8.

15. If p varies inversely as the square root of q, and p = 12 when q = 36, find p when q = 16.

16. If w is jointly proportional to u and v, and w =2 when u=4 and v=6, what is w when u=3 and v=8?

17. Suppose that r varies directly as p and inversely as q2, and that r = 27 when p = 3 and q = 2. Find r when p = 2 and q = 3.


18. By Ohm's law The current flowing in a wire is inversely proportional to the resistance of the wire. If the current is 5 amperes (A) when the resistance is 24 ohms (Ω), for what resistance will the current be 8 amperes?


19. The conductance of a wire varies directly as the square of the wire's diameter and inversely as its length. Fifty meters of wire with a diameter 2 mm has a conductance of 0.12 ohms. If a wire of the same material has length of 75 m and diameter of 2.5 mm, what is its conductance?

20. If p is inversely proportional to q, and p = 28 when q = 1.5, find q when p = 7.  

Answer
8. 575/0.39 = 810/x so x = 0.55
14. 32(1.5) = 8r so r = 6
15. 12(36)^1/2 = p(16)^1/2 so p = 18
16. 2/(4*6) = w/(3*8) so w = 2
17. I presume you mean q^2.  (27)(2^2)/3 = r(3^2)/2 so r = 8
18. 5(24) =8R so R = 15 ohms
19. conductance has units of mhos, not ohms, so I assume you mean 0.12 mhos.  (0.12)(50)/2^2 = C(75)/(2.5)^2 so C = 0.125 mhos
20. (28)(1.5) = q(7) so q = 6