Remainder of product divided by 100
Question
What is the remainder when 85 × 87 × 89 × 91 × 95 × 96 is divided by 100?
Options
0
1
2
4
Explanation
To check for a remainder of 0 modulo 100, analyze the prime factors 2 and 5 within the continuous product expression : 85 = 5 × 17 \implies contains one factor of 5. 95 = 5 × 19 \implies contains one factor of 5. Total factors of 5 from these two odd numbers = 5 × 5 = 25.
Now scan for even terms: 96 = 32 × 3 = 2^5 × 3 \implies contains multiple factors of 2, specifically a multiple of 4.
Multiplying our extracted factors yields: ⟨MATH⟩25 × 4 = 100⟨/MATH⟩. Because the product contains 100 as an explicit factor, the entire expression is perfectly divisible by 100, leaving a remainder of exactly 0.
Answer: (a).
Question details
Year
2023
Paper
CSAT
Question
Q7
Section
Numerical Ability
Sub-topic
Remainders
Type
Number theory
Difficulty
Medium
Source hint
Number theory
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