SOLUTION: Freddie the frog is climbing up a well. Everyday he climbs up 3 m but some nights he falls asleep and slips back 4m. At the start of the sixteenth day, he has climbed a total of 29

Algebra ->  Equations -> SOLUTION: Freddie the frog is climbing up a well. Everyday he climbs up 3 m but some nights he falls asleep and slips back 4m. At the start of the sixteenth day, he has climbed a total of 29      Log On


   



Question 766648: Freddie the frog is climbing up a well. Everyday he climbs up 3 m but some nights he falls asleep and slips back 4m. At the start of the sixteenth day, he has climbed a total of 29m. On how many nights was he asleep?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
One time period is a day and a night
The frog either advance by +3m or
falls back +3+-+4+=+-1+m
----------------------
Let +a+ = number of periods of +3m gain
Let +b+ = number of periods of -1m loss
----------------------
(1) +a+%2B+b+=+15+ ( the 16th day hasn't happened yet )
(2) +3a+-+b+=+29+
------------------
Add the equations
+4a+=+44+
+a+=+11+
and
(1) +11+%2B+b+=+15+
(1) +b+=+4+
------------
The frog slept 4 nights
check:
(2) +3a+-+b+=+29+
(2) +3%2A11+-+4+=+29+
(2) +33+-+4+=+29+
(2) +29+=+29+
OK