1.

If m and n are positive integers, then the digit in the units' place of 5n + 6m is always (a) 1 (b) 5 (c) 6 (d) n + m

Answer»

(a) 1

The units' digit of any positive integer power of 5 is always 5 and that of any positive integral power of 6 is always 6. 

\(\therefore\) Units’ digit of 5m + 6n = Units' digit of (5 + 6) 

= Units' digit of 11 = 1.



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