The least positive remainder when \(17^{30}\) is divided by 5 is (a) 2 (b) 4 (c) 3 (d) 1

Short Answer

Expert verified
The least positive remainder when \(17^{30}\) is divided by 5 is (b) 4.

Step by step solution

01

Find the remainder when the base is divided by 5

We want to find the remainder when 17 is divided by 5. We have: \[17 \equiv 2 \pmod 5\]
02

Raise the remainder to the power of 30

Now, we raise the remainder obtained in step 1 (which is 2) to the power of 30: \[2^{30}\] Note that we are not directly computing the value of \(2^{30}\), but rather, finding the remainder when it is divided by 5.
03

Determine the pattern of powers of 2 modulo 5

To find the remainder when \(2^{30}\) is divided by 5, we start by observing the powers of 2 modulo 5: \(2^1 \equiv 2 \pmod{5}\), \(2^2 \equiv 4 \pmod{5}\), \(2^3 \equiv 3 \pmod{5}\), \(2^4 \equiv 1 \pmod{5}\) We notice that there is a pattern that repeats every 4 powers, i.e., \((\)2, 4, 3, 1)$.
04

Find the remainder in the pattern of powers

Since we have discovered in step 3 that the powers of 2 modulo 5 repeat every 4 powers, we can find the remainder when \(2^{30}\) is divided by 4: \[30 \div 4 = 7 \text{ with a remainder of } 2\] Using the remainder (2), we know that it corresponds to the second number in the \((\)2, 4, 3, 1)$ pattern. Therefore: \[2^{30} \equiv 4 \pmod 5\]
05

Answer

Based on our calculations, the least positive remainder when \(17^{30}\) is divided by 5 is 4. Hence, the correct answer is: (b) 4

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