missing tally

Question

You are making a report on the number of inside and outside calls handled by a particular switchboard. Over a 15 day period, the total number of all inside and outside calls handled by the switchboard was 5,760. The average number of inside calls per day was 234. You cannot find one day's tally of outside calls, but the total number of outside calls for the other fourteen days was 2,065. From this information, how many outside calls must have been reported on the missing tally?

Answer 1

Total calls handled in 15 days = outside + inside calls = 5,760

Inside calls = 234 x 15 days = 3,510

14 days outside calls = 2,065

 

Add the inside calls for 15 days and the 14 day outside calls:

3,510 + 2,065 = 5,575

 

To find the missing tally simply subtract the above number from the total number of calls handled:

5,760 - 5,575 = 185 outside calls should be reported for the missing tally. 

 

Answer 2

Total # of inside and outside calls = 5,760

Total # of outside calls for 14 days = 2,065

 

Total # of inside calls = (# of days) x (average # of inside calls per day) = 15 x 234 = 3,510

 

(Total # of inside and outside calls) = (Total # of inside calls) + (Total # of outside calls)

⇒ 5,760 = 3,510 + (Total # of outside calls)

⇒ (Total # of outside calls) = 5,760 - 3,510 = 2,250

 

(# of missing outside calls) = (Total # of outside calls for 15 days) - (Total # of outside calls for 14 days)

⇒ 2,250 - 2,065 = 185

 

185 outside calls were made on that missing day.