Bunuel
When n is divided by 24, the remainder is 5. What is the remainder when 3n is divided by 8?
A. 3
B. 4
C. 5
D. 6
E. 7
One method of doing this is by assuming a value for n.
Say n = 5. When 5 is divided by 24, remainder is 5.
3n = 15. When 15 is divided by 8, reminder is 7.
Answer (E)
The other is based on your division as grouping concepts.
n balls can be split into groups of 24 and there will be 5 remaining balls. 3n will have thrice the number of groups of 24 balls and 3 groups of 5 balls each i.e. 15 balls remaining. When you divide this by 8, each group of 24 balls will evenly split into groups of 8 balls each and out of 15 remaining balls, you will be able to make another group of 8. You will be left with 7 balls.
For more on grouping, check this link:
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2011/04 ... unraveled/Answer (E)