I tried something slightly different. Would really appreciate any input on whether I'm correct on this train of thought.
\frac{43^86}{5} can be written as \frac{[45 + (-2)]^86}{5}. Since 45 can be fully divided with 5, we ignore it.
So the question stands as: what is the remainder of 2^86/5. Following the cyclicity rule, we know that 2^86 has a units digit of ..4.
Every number that ends in 4 and is divided by 5, gives a remainder of 4, so answer is E.
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- GMAT Prep #1 CAT (Apr 2019) : 640 (Q48, V30)
- GMAT Prep #1 CAT (early Oct 2019 - post hiatus) : 680 (Q48, V34)
- MGMAT CAT #1 (mid Oct 2019) : 640 (Q44, V34)
- MGMAT CAT #2 (mid-to-late Oct 2019) : 610 (Q40, V34)
- GMAT Prep #2 CAT (late Oct 2019) : 720 (Q49, V40)
- MGMAT CAT #3 (early Nov 2019) : 660 (Q42, V38)
- GMAT 1 : 700 (Q49, V35)
Still not there.
If you're reading this, we've got this.