Question

The unit's digit of the result of the following expression is
(49 × 49) + ( 65 × 65) + (84 × 84)

• A. 4
• B. 2
• C. 1
• D. 0

Answer 1

The correct option is B 2

As the square of any number ending with 9 has 1 in it unit's place, (49 × 49) has 1 in its unit's place.
Similarly, ( 65 × 65) has 5 in its unit's place
Similarly, ( 84 × 84) has 6 in its unit's place.

Now adding all the three numbers in unit's places to get the unit's place digit of the given expression, 1 + 5 + 6 = 12.

Here 2 is present in the unit's place and this is only the unit's digit in the result of the given expression.