What is the units' digit of the following expression ?
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Official Explanation
We are tasked with finding the units digit of the expression:
To find the units digit, we only need to focus on the units digits of the individual terms. Let's break it down step by step:
Step 1: Units digit of
The units digit of is the same as the units digit of , because ends in a 2.
Now, we calculate the units digit of . The powers of 2 cycle every 4 terms in their units digits:
So, the units digit of is 2.
Step 2: Units digit of (14)^4[/m]
The units digit of is the same as the units digit of , because ends in a 4.
Now, we calculate the units digit of . The powers of 4 cycle every 2 terms in their units digits:
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good question
Amazing
What it tests
Your command of divisibility, primes, factors, parity, and how the GMAT tests properties of integers.
Common trap
Forgetting that 1 is not prime, that 0 is divisible by every integer, or that negative numbers flip your assumptions.