Correct answer is: a) 10.5

Explanation

The product of two number is 5.25.
Their HCF be 0.5.
We know,
HCF \times LCM = Product of Two Number
\rightarrow 0.5\times LCM = 5.25
\rightarrow LCM =\large\frac{5.25}{0.5}
\rightarrow LCM =\left(\frac{525\times10}{5\times100}\right) _{[Remove Decimal]}
\rightarrow LCM =10.5
So that, their LCM is 10.5.
Ans: 10.5 is the LCM of two numbers.

Other variants of this particular math question are:

1. If the product of two numbers is 5.25 and their highest common factor (HCF) is 0.5, what is their least common multiple (LCM)?
2. Given that the product of two numbers is 5.25 and their greatest common divisor (GCD) is 0.5, what is their lowest common multiple (LCM)?
3. When the product of two numbers equals 5.25 and their highest common factor (HCF) is 0.5, what is their least common multiple (LCM)?