Four bells toll at intervals of $8$,$12$,$15$,and $18$ seconds respectively. All four begin to toll together. How many times will they toll together in one hour,excluding the one at the start?

Write the denominator of the rational number $\frac{257}{5000}$ in the form $2^{m} \times 5^{n},$ where $m, n$ are non-negative integers. Hence,write its decimal expansion,without actual division.

On a morning walk,three persons step off together and their steps measure $40\, cm$,$42\, cm$ and $45\, cm$,respectively. What is the minimum distance each should walk so that each can cover the same distance in complete steps? (in $cm$)

"The product of two consecutive positive integers is divisible by $2$." Is this statement true or false? Give reasons.

Prove that the following number is irrational: $\sqrt{11}$

The following real number is expressed in decimal form. Determine whether it is rational or not. If it is rational,express it in the form of $\frac{p}{q}$. $3.127$