Two identical strings $X$ and $Z$ made of same material have tension $\mathrm{T}_{\mathrm{x}}$ and $\mathrm{T}_{\mathrm{z}}$ in them. If their fundamental frequencies are 450 Hz and 300 Hz , respectively, then the ratio $\mathrm{T}_{\mathrm{x}} / \mathrm{T}_{\mathrm{z}}$ is
