gistfile1.py

#!/usr/bin/env python3

import math

def ex1():
	return '%0.3f' % (4 * math.pi * math.pow(5, 3) / 3.0)

def ex2():
	return '$%0.2f' % (60*(24.95 * (1 - 0.4)) + 3.00 + 0.75*59)

def ex3():
	def time_to_mins(t):
		hr, mn = [int(x) for x in t.split(':')]
		return hr*60 + mn
	def mins_to_time(m):
		h = int(m / 60)
		return '%d:%d' % (h, m - h*60)
	def rate_in_mins(r):
		m, s = [int(x) for x in r.split(':')]
		return m + s/60.0
	return mins_to_time(time_to_mins('6:52') + rate_in_mins('8:15')*2 + rate_in_mins('7:12')*3)

print('Exercise 2.4')
print('    1: %s' % ex1())
print('    2: %s' % ex2())
print('    3: %s' % ex3())