```ts
/**
 * Calculates and returns the number of whole hours from a given count of minutes.
 *
 * @param minutes - The total number of minutes to convert into hours.
 * @returns The number of whole hours in the input time period.
 */
export function durHours(minutes: number): number {
  if (minutes < 0) throw new Error('Input cannot be negative.');
  return Math.floor(minutes / 60);
}

/**
 * Converts a count of minutes into its equivalent as hours and minutes, formatted as 'hh:mm'.
 *
 * @param minutes - The total number of minutes to convert.
 * @returns A string representing the time in 'hh:mm' format.
 */
export function durText(minutes: number): string {
  const hours = Math.floor(minutes / 60);
  const remainingMinutes = minutes % 60;
  return `${hours.toString().padStart(2, '0')}:${remainingMinutes.toString().padStart(2, '0')}`;
}
```