Problem:
Suppose that 4a=5,5b=6,6c=7, and 7d=8. What is a⋅b⋅c⋅d?
Answer Choices:
A. 1
B. 23
C. 2
D. 25
E. 3
Solution:
Because
4a⋅b⋅c⋅d=(((4a)b)c)d=((5b)c)d=(6c)d=7d=8=43/2
we have a⋅b⋅c⋅d=23.
Answer: B.
The problems on this page are the property of the MAA's American Mathematics Competitions