Problem: The symbol 25b​ represents a two-digit number in the base b. If the number 52b​ is double the number 25b​, then b is:
Answer Choices:
A. 7
B. 8
C. 9
D. 11
E. 12
Solution:
52b​=5 b+2,25b​=2 b+5. Since 52b​=2(25b​),5 b+2=2(2 b+5)∴b=8