Ratio of rainfall on Monday and Friday = 20x : 21x Total rainfall on Monday, Tuesday, Wednesday and Thursday = 420.5 × 4 = 1,682 cm Total rainfall on Tuesday, Wednesday, Thursday and Friday = 440.5 × 4 = 1,762 cm Total rainfall on Friday - Monday = 1,762 - 1,682 = 80 cm. Ratio of rainfall on Monday and Friday = 20x : 21x 21x−20x=80 x=80 Rainfall on Monday =20x=20×80=1600 cm Rainfall on Friday =21x=21×80=1680cm