Which among
Question:

Which among 432 , 672 , 522 , 592 would end with digit 1?

(a) 432

(b)672

(c)522

(d)592

Solution:

(d) We know that, the unit’s digit of the square of a natural number is the unit’s digit of the

square of the digit at unit’s place of the given natural number.

$\therefore$ Unit’s digit of $43^{2}=9 \quad\left[\because 3^{2}=9\right]$

Unit’s digit of $67^{2}=9$  $\left[\because\right.$ unit’s digit of $7^{2}$ is 9$]$

Unit’s digit of $52^{2}=4$ $\left[\because 2^{2}=4\right]$

Unit’s digit of $59^{2}=1$ $\left[\because\right.$ unit’s digit of $9^{2}$ is 1$]$

Clearly, the square of 59 end with digit $1 .$