GMAT Practice Question: What is the remainder when 3^{24} is divided by 5 ?
Question
What is the remainder when 3^{24} is divided by 5 ?
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Topics: remainders, exponents, number theory
Solution
Step 1
We translate the phrase \textbf{"remainder when 3^{24} is divided by 5"} into an equation relating the divisor, quotient, and remainder.
5k + r = 3^{24}
Step 2
We calculate the remainder when 3^4 is divided by 5, since we will use that to simplify 3^{24}.
3^4 = 81 = 5\times16 + 1 \text{remainder of }3^4\text{ divided by }5 = 1
Step 3
We express 3^{24} as (3^4)^6 and use the remainder of 3^4 to find the remainder of the entire expression.
3^{24} = (3^4)^6 = (5\times16 + 1)^6 \text{remainder }= 1^6 = 1
Answer
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