Problem: The number (248−1) is exactly divisible by two numbers between 60 and 70. These numbers are
Answer Choices:
A. 61,63
B. 61,65
C. 63,65
D. 63,67
E. 67,69
Solution:
Two factors are 63 and 65 because 248−1=(224−1)(224+1)=(212−1)(212+1) (224+1)=(26−1)(26+1)(212+1)(224+1)=63×65(212+1)(224+1).