Chapter 8.3, Problem 8P

For each of the numbers in (a) through (d), verify that the divisibility test for 9 accurately predicts which numbers are divisible by 9.

Example: 52,371 is divisible by 9 because $52,371÷9$ is the whole number 5819, with no remainder. The sum of the digits of $52,371—namely,5+2+3+7+1=18—$ is also divisible by 9.

a. 1,827,364,554,637,281

b. 2,578,109

c. 777,777

d. 777,777,777