Average Practice Test 1

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
$21\mathit{x}-20\mathit{x}=80$
$\mathit{x}=80$
Rainfall on Monday $=20\mathit{x}=20\times 80=1600$ cm
Rainfall on Friday $=21\mathit{x}=21\times 80=1680$cm