CBSE2026Class Class 10 · Mathematics1 Marks · Mcq✅ Verified
If the HCF of two positive integers $a$ and $b$ is 1, then their LCM is :
A. $a+b$
B. $a$
C. $b$
D. $ab$
✅ Answer & Solution
✅ Correct Answer: D
Step 1: For any two positive integers, the product of HCF and LCM equals the product of the numbers.
$$\text{HCF}(a,b)\times \text{LCM}(a,b)=a\times b$$
Step 2: Here $\text{HCF}(a,b)=1$ (i.e. $a$ and $b$ are co-prime).
$$1\times \text{LCM}(a,b)=ab$$
Step 3: Therefore $\text{LCM}(a,b)=ab$.
Hence the correct option is (D) $ab$.
