Question
The units digit of the expression $25^6251 + 36^528 + 73^54$ is
Answer: Option A
Answer: (a)Unit digit in the expansion of $25^6251$= Unit digit in the expansion of $5^6251$ = 5$36^528$≡ Unit digit in $6^528$ = 6Now, $3^1 = 3; 3^2 = 9; 3^3 = 27; 3^4 = 81; 3^5 = 243 ;$.... $73^54 = 73^52 × 73^2$≡ $3^2$ = 9 Required digit = Unit’s digit of the sum 5 + 6 + 9 = 0
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Answer: (a)Unit digit in the expansion of $25^6251$= Unit digit in the expansion of $5^6251$ = 5$36^528$≡ Unit digit in $6^528$ = 6Now, $3^1 = 3; 3^2 = 9; 3^3 = 27; 3^4 = 81; 3^5 = 243 ;$.... $73^54 = 73^52 × 73^2$≡ $3^2$ = 9 Required digit = Unit’s digit of the sum 5 + 6 + 9 = 0
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