Answer

Correct Answer : d ) 0

Quick Approach

Consider the given expression

4²⁸⁷ * 397²⁴ * 71⁵⁴ * 25⁹⁷

As ‘25’ will give ‘5’ at the unit place so ‘5’ multiplied by any other even number will result in zero at the unit place.

Hence, (d) is the correct answer.

Basic Approach

Consider the given expression

4²⁸⁷ * 397²⁴ * 71⁵⁴ * 25⁹⁷

We solve these types of questions by checking the cyclicity of the numbers.

Cyclicity of a number means that after how many powers of that number unit digit gets repeated.

Cyclicity of 4 is 2 i.e. after an interval of two powers, we get the same unit digit. Unit digit of 41 is 4, 42 is 6, and 43 is again 4.

Similarly, cyclicity of 7 is 4, cyclicity of 1 is 1, cyclicity of 5 is 1

Thus, unit digit of 4²⁸⁷ * 397²⁴ * 71⁵⁴ * 25⁹⁷ will be

⇒ Unit digit of 4²⁸⁷ * 7²⁴ *1⁽⁵⁴⁾ * 5⁽⁹⁷⁾ 

Using the cyclicity of the given numbers, we get

⇒ Unit digit of (4³ * 7⁴ * 1 * 5)

⇒ Unit digit of (4 * 1 * 1 * 5) = 0

Hence, (d) is the correct answer.

Such type of question is asked in various government exams like SSC CGL, SSC MTS, SSC CPO, SSC CHSL, RRB JE, RRB NTPC, RRB GROUP D, RRB OFFICER SCALE-I, IBPS PO, IBPS SO, RRB Office Assistant, IBPS Clerk, RBI Assistant, IBPS RRB OFFICER SCALE 2& 3, UPSC CDS, UPSC NDA, etc.

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