Problem:
Which of the following is equal to
21​−31​31​−41​​?
Answer Choices:
A. 41​
B. 31​
C. 21​
D. 32​
E. 43​
Solution:
The least common multiple of 2,3, and 4 is 12 , and
21​−31​31​−41​​⋅1212​=6−44−3​=(C)21​​
The problems on this page are the property of the MAA's American Mathematics Competitions