The LCM and HCF of the numbers $42$ and $49$ are in the ratio of:

Prime factorization of the numbers:
$$42=2\times 3\times 7$$

$$49=7\times 7=7^2$$

Highest Common Factor (HCF):

$$\text{HCF}(42,49)=7^1=7$$

Lowest Common Multiple (LCM):

$$\text{LCM}(42,49)=2^1\times 3^1\times 7^2=2\times 3\times 49=294$$

Ratio of LCM to HCF:

$$\text{Ratio}=\frac{\text{LCM}}{\text{HCF}}=\frac{294}{7}=\frac{42}{1}$$

Thus, the ratio is $42:1$.