345 * 60 = 20700. So it converts to 20700 ft/hr
Roll 1: 1 number out of 6 total numbers = 1/6
Roll 2: 1 number out of 6 total numbers = 1/6
Roll 3: 1 number out of 6 total numbers = 1/6
Roll 4: 1 number out of 6 total numbers = 1/6
Roll 1 AND Roll 2 AND Roll 3 AND Roll 4
1/6 x 1/6 x 1/6 x 1/6 = 1/1296
Let the original bill be

, then the final bill after the charges been added are

, where

is the increase in the bill by 0.2 (100%+20% = 120% = 1.2)
The range of the original bill is
200 <

< 800, subtract each term by 25
175 <

< 775, divide each term by

145.83 <

< 645.83
Hence, the range of the original bill is between $145.83 and $645.83
-0.8 = -0.8/10
-0.8 x 10 = -8
<span>1 × 10 = 10</span>
<span>-8/10
Simplified = -4/5
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