Transcript Slide 1

Estimation
MATH 102
Contemporary Math
S. Rook
Overview
• Section 1.3 in the textbook:
– Estimation & Rounding
Estimation & Rounding
Estimation & Rounding
• Estimation: the process of using numbers that
are easier to work with to get a feeling for an
answer
– Often accomplished by using rounding
• Review of rounding:
– Down if the previous digit is 4 or lower
• e.g. 123.456
– Up if the previous digit is 5 or higher
• e.g. 123.456
– Can cascade (i.e. carry through several numbers)
• e.g. 1,299,999 ; 1998 ; 239,924
Estimation & Rounding (Continued)
• Consider computing 407 / 7
– Before doing the long division, estimate the
answer
– Pick nearby values for the numbers that make the
computation convenient
Estimation (Example)
Ex 1: Suppose that you made the following
purchases today: $21.60 for dinner, $39.93 for
groceries, $191 for textbooks, $42.50 for gas
a) Estimate the total of your purchases by
rounding to the nearest (1) ten dollars (2) dollar
(3) ten cents
b) What is the actual total of your purchases
today? Which estimate comes the closest?
Estimation (Example)
Ex 2: At a certain college, suppose that 15% of
all grades are ‘A’s, 25% are ‘B’s, 35% are ‘C’s,
15% are ‘D’s, and 10% are ‘F’s. If there are
9445 grades:
a) Approximately how many ‘A’s were there?
b) Approximately how many total ‘B’s, ‘D’s,
and ‘F’s were there?
Estimation (Example)
Ex 3: For an executive party, the caterer decides
to purchase giant cookies so that each
executive gets one cookie. If each cookie
costs $1.85 and there are 28 executives at the
party, approximately how much will be spent
on the cookies?
Summary
• After studying these slides, you should know
how to do the following:
– Round a number to any specified place
– Use rounding to solve application problems
– Use estimation to solve application problems
• Additional Practice:
– See the list of suggested problems for 1.3
• Next Lesson:
– The Language of Sets (Section 2.1)