The HCF of two numbers is 12, and their LCM is 144. If one number is 36, what is the other?
72
- Step 1: Relation between HCF, LCM, and product - For two positive integers $a$ and $b$: \[ \text{HCF}(a,b) \times \text{LCM}(a,b) = a \times b \]
- Step 2: Substitute known values - \[ 12 \times 144 = 36 \times b \]
- Step 3: Solve for $b$ - \[ b = \frac{12 \times 144}{36} = \frac{1728}{36} = 48 \]
- Step 4: Verification - HCF(36, 48) = 12, LCM(36, 48) = $\frac{36 \times 48}{12} = 144$. Both match the given.
- Step 5: Conclusion - The other number is $48$, matching option (2).
For any natural number $k$, let $a_k = 3^k$. The smallest natural number $m$ for which \[ (a_1)^1 \times (a_2)^2 \times \dots \times (a_{20})^{20} \;<\; a_{21} \times a_{22} \times \dots \times a_{20+m} \] is: