CUET UG Mathematics Applied Logarithms And Indices Previous Year Questions (PYQs)
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The number at unit place of number $17^{123}$ is:
1
2
3
4
Solution
Unit digit depends on $7^{123}$
Cycle of unit digits of powers of 7:
$7^1=7$
$7^2=49$ → 9
$7^3=343$ → 3
$7^4=2401$ → 1
Cycle repeats every 4.
Now,
$123 \mod 4$
$123=4\times 30+3$
Remainder = 3
So unit digit same as $7^3$
Unit digit = 3
CUET UG Mathematics Applied
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CUET UG Mathematics Applied
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