The HCF and LCM of two numbers $\mathrm{x}$ and $\mathrm{y}$ are respectively 6 and 210 .

If $x+y=72$, then $\frac{1}{x}+\frac{1}{y}$ is equal to :

If the LCM of two numbers is 12 times their HCF and the sum of LCM and HCF is 403, and one number is 93, find the other number.

The HCF of $(\frac{9}{10}, \frac{12}{25}, \frac{18}{35}, \frac{21}{40})$ is

The traffic lights at three different road crossings change after every 48 sec, 72 sec and 108 sec, respectively. They all change simultaneously at 08:20:00 hours, when will they again change simultaneously?

Let $x$ be the least number which when divided by $8, 12, 20, 28, 35$ leaves a remainder of $5$ in each case, then the sum of digits of $x$ is :

The product of two positive integers $x$ and $y$ is 6760 and their HCF is 13. How many such pairs $(x, y)$ can be formed?