Bunuel
Twenty people had dinner together at a restaurant. The cost of the meal plus an automatic gratuity of 18% for a large party was $531.00, before sales tax was added. What was the average price of the meal per person NOT INCLUDING the gratuity or sales tax?
(A) $21.77
(B) $22.50
(C) $26.55
(D) $30.50
(E) $36.55
Given:
20 people,
Total cost + 18 % Gratuity = 531
Need to find per person cost excluding the gratuity...
Method 1: Normal Calculations
average total cost will be less than average of total Cost + 18% Gratuity
=> average of total cost + Gratuity = 531/20
=> \(total cost < 531/20\)
=> total cost < 26.55
eliminate option C, D and E
Gratuity is little less than 20%
so for ease of calculation lets take gratuity as 20%
=> Average Total cost * 1.20 (20% gratuity) = Average (total cost + Gratuity)
=> \(Average total cost = 26.55/1.20\)
Approx = 22
as we increased the denominator from 1.18 to 1.2 the answer should be greater than 22 hence Option B
Method 2: Use the options
Pick the mid value -> 26.55
if that is the average cost than overall cost = 26.55 * 20 = 513.00,
Now 18% gratuity will result in an amount that is more than 531 hence all options equal to or greater than 26.55 are disqualified
move on to the next number 22.50
22.50 * 20 = 450
increase by 18% = 450 *1.18 = 531
this is what we were looking for hence answer is B
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