These are sample practice MCQs created for exam preparation. These are NOT official exam questions.
What is the units digit of 13^87 × 17^93?
Question:
What is the units digit of 13^87 × 17^93?
What is the units digit of 13^87 × 17^93?
Options
Answer: (E) 9
Explanation:
Units digit of 13^87: powers of 3 are 3,9,7,1,3,9,7,1... (period 4). 87 mod 4 = 3, so units digit is 7. Units digit of 17^93: powers of 7 are 7,9,3,1,7,9,3,1... (period 4). 93 mod 4 = 1, so units digit is 7. Product: 7 × 7 = 49, units digit is 9.
Explanation:
Units digit of 13^87: powers of 3 are 3,9,7,1,3,9,7,1... (period 4). 87 mod 4 = 3, so units digit is 7. Units digit of 17^93: powers of 7 are 7,9,3,1,7,9,3,1... (period 4). 93 mod 4 = 1, so units digit is 7. Product: 7 × 7 = 49, units digit is 9.
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