The relationship between the Highest Common Factor (HCF) and the Least Common Multiple (LCM) of two numbers is given by the formula:

$\text{HCF} \times \text{LCM} = \text{Product of the two numbers}$

In this case, the numbers are 36 and 90, and the HCF is 18. Let $\text{LCM}$ be $x$.

$18 \times x = 36 \times 90$

First, calculate the product of 36 and 90:

$36 \times 90 = 3240$

Now, solve for $x$:

$x = \frac{3240}{18} = 180$

Thus, the Least Common Multiple (LCM) of 36 and 90 is 180.

Would you like any further details or explanations?

Here are 5 related questions:

1. How do you find the HCF using prime factorization?
2. Can you explain how the relationship between HCF and LCM works in more detail?
3. What is the LCM of 45 and 60?
4. How can you find the LCM if the HCF is not given?
5. What is the difference between HCF and LCM?

Tip: The HCF is always a divisor of the LCM.