QUESTION

CSAT

Hard

Maths

Prelims 2022

What is the remainder when 91×92×93×94×95×96×97×98×9991 \times 92 \times 93 \times 94 \times 95 \times 96 \times 97 \times 98 \times 99 is divided by 1261?

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Explanation

To solve this question, we can apply divisibility tests. Start by checking 1261 for divisibility by prime numbers.

First, 2, 3, and 5 can be easily ruled out as divisors. Next, we check divisibility by 13. Dividing 1261 by 13 gives 97, which is a prime number.

Thus, the prime factorization of 1261 is: 1261=13×971261 = 13 \times 97

Now, observe that 91 is divisible by 13. Additionally, 97 is already a factor of 1261, meaning that 1261 will divide the expression (91×92×93×94×95×96×97×98×99)(91 \times 92 \times 93 \times 94 \times 95 \times 96 \times 97 \times 98 \times 99) completely.

Therefore, the remainder when this product is divided by 1261 is 0.

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