Question

Unit's digit of the number
$3^{1001}\times 7^{1002}\times {13}^{1003}$ is

• A. $1$
• B. $3$
• C. $7$
• D. $9$

Answer 1

The correct option is D $9$

Units digit in $3^4=1$
Units digit in $7^4=1$
Units digit in ${13}^4=1$
Thus,
Units digit of $3^{1001}\times 7^{1002}\times {13}^{1003}$
Units digit $=3^{250\times 4+1}+7^{250\times 4+2}+{13}^{250\times 4+3}$
Units digit $=(1\times 3)(1\times 9)(1\times 7)$
Units digit $=3\times 9\times 7$
Units digit $=9$
Hence, option 'D' is correct.