WHY WORK BACKWARDS

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• WHY WORK BACKWARDS?
• Sometimes a mathematician must make a series of
  computations, starting with data presented at the
  end of the problem and ending with data presented
  at the beginning of the problem.
• With problems related to time, a mathematician
  may know what time the situation ends, but may
  need to use information in the problem to
  calculate what time the situation begins.

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• HOW DO YOU WORK BACKWARDS?
• Recognize what information you already know.
• Identify what you are trying to find out.
• Think about what information in the problem can
  help you calculate what you want to find out.
• WARNING!!!
• Be careful to keep track of what the numbers
  represent. It can get confusing!!!

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WORK BACKWARDS
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Sample ProblemsWORK BACKWARDS
Farmer Bill has cows, horses and chickens on his
farm. There are 6 more cows than horses, and
double the number of chickens than horses. There
are 20 chickens on Farmer Bill's farm. How many
cows are on his farm? Jane took a bus from
Silver Spring to Mucky Mountain. After 2 hours,
the bus made the first stop. A half hour later it
stopped for the second time. 1 hour later it
stopped for the third time. Finally, they reached
Mucky Mountain three and a half hours later at
1100 p.m. What time did Jane leave Silver
Spring?