EXAMPLE:In a conference center, the Mountain View Room can seat 78
people, the Lake View Room can seat 32 people, and the Trail View Room
can seat 46 people. Find the total number of people that can be seated at any
one time.
SOLUTION:
GOAL: You are being asked to find the total number of people that can be
seated.
STRATEGY: Use addition since you need to find a total and all the items in
the problem are the same (i.e., people).
IMPLEMENTATION: 78þ 32 þ 46 ¼156.
EVALUATION: The conference center can seat 156 people. This can
be checked by estimation. Round each value and then find the sum:
80 þ 30 þ 45 ¼155. Since the estimated sum is close to the actual sum, you
can conclude that the answer is probably correct. (Note:When using estima-
tion, you cannot be 100% sure your answer is correct since you have used
rounded numbers.)
Usesubtractionwhen you are asked to find
how much more,
how much less,
how much larger,
how much smaller,
how many more,
how many fewer,
the difference,
the balance,
how much is left,
how far above,
how far below,
how much further, etc.,and all the items in the problems are the same type.
EXAMPLE:If Lake Erie is 241 miles long and Lake Huron is 206 miles long,
how much longer is Lake Erie than Lake Huron?
LESSON 2 Using Whole Numbers 7