What is the unit digit of the product of all the prime numbers
What is the unit digit of the product of all the prime numbers between 51 and 78?
51 और 78 के बीच सभी अभाज्य संख्याओं के गुणनफल का इकाई अंक क्या है?
Detailed Solution & Logic
Correct Answer:
7
Prime numbers between 51 and 78: 53, 59, 61, 67, 71, 73
Unit digits: 3, 9, 1, 7, 1, 3
$ 3 \times 9 = 27 $
$ 7 \times 1 = 7 $
$ 7 \times 7 = 49 \Rightarrow 9 $
$ 9 \times 1 = 9 $
$ 9 \times 3 = 27 \Rightarrow 7 $
Unit digit of the product = 7
Answer = 7
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