M7MBA wrote:A function V(a, b) is defined for positive integers a, b and satisfies
V(a, a) = a,
V(a, b) = V(b, a),
V(a, a+b) = (1 + a/b) V(a, b).
The value represented by V(66, 14) is?
(A) 364
(B) 231
(C) 455
(D) 472
(E) None of the foregoing
First, we need to mention that with the three formulas given, we always want to express V(b, a) as V(a, b) whenever b > a. Thus we can simplify the expression continuously until it reaches a point where the two numbers for the function are the same.
Next, notice that in the last formula, we have: V(a, a+b) = (1 + a/b) V(a, b) = (a+b)/b V(a, b). If we let c = a + b (we see that c > a), then V(a, c) = c/(c - a) V(a, c - a). So we’ll be using this formula instead of V(a, a+b) = (1 + a/b) V(a, b) in our calculations that follows. Now let’s begin.
Using the second property, we have: V(66, 14) = V(14, 66). So
V(14, 66) = 66/52 V(14, 52) (note: recall that V(a, c) = c/(c - a) V(a, c - a) when c > a)
V(14, 52) = 52/38 V(14, 38)
V(14, 38) = 38/24 V(14, 24)
V(14, 24) = 24/10 V(14, 10) = 24/10 V(10, 14)
V(10, 14) = 14/4 V(10, 4) = 14/4 V(4, 10)
V(4, 10) = 10/6 V(4, 6)
V(4, 6) = 6/2 V(4, 2) = 6/2 V(2, 4)
V(2, 4) = 4/2 V(2, 2)
V(2, 2) = 2
So we have:
V(14, 66) = 66/52 * 52/38 * 38/24 * 24/10 * 14/4 * 10/6 * 6/2 * 4/2 * 2 = 66 * 14 * 1/2 = 462
Answer: E