**Question:**

If two positive integers a and b are written as a = x3y2 and b = xy3, wfiere x, y are prime numbers, then HCF (a, b) is

(a) xy

(b) xy2

(c)x3y3

(d) xy2

**Solution:**

(b) Given that, $\quad a=x^{3} y^{2}=x \times x \times x \times y \times y$

and $\quad b=x y^{3}=x \times y \times y \times y$

$\therefore$ HCF of $a$ and $b \quad=\operatorname{HCF}\left(x^{3} y^{2}, x y^{3}\right)=x \times y \times y=x y^{2}$

[since, HCF is the product of the smallest power of each common primè facter involved in the twimbers]