Transcript Estimating with Fractions

Estimating with Fractions
QuickTime™ and a
TIFF (Uncompress ed) dec ompres sor
are needed to s ee this pic ture.
Math humor:
Pilot: I flew about 3/4 of the way across
the Atlantic and then noticed I didn’t
have enough fuel to make it across.
So, I flew back to get more fuel.
Talking/do not write it down
Sometime, when solving problems, you may
not need an exact answer. To estimate
sums and differences of fractions and mixed
numbers, round each fraction to 0, 1/2, or 1.
You can use a number line to help.
1
Benchmarks for Rounding
Write all this down
Fractions
Round to 0 if the
numerator is
much smaller
than the
denominator
Round to 1/2 if
the numerator
is about half the
denominator.
Round to 1 if the
numerator is
nearly equal to
the denominator.
Examples:
1/ , 3 / , 2/
9
20
11
Examples:
2/ , 5/ , 7/
5
12
13
Examples:
8/ , 23/ , 97/
9
25
100
Qui ckTime™ and a
TIFF (U ncompr essed) decompressor
are needed to see thi s pi cture.
Examples:
A) One of the largest lobsters
ever caught weighed 44 3/8 lb.
Estimate how much more this
lobster weighed than an
average 3 lb lobster.
44 3/8 - 3
44 3/8 --> 44 1/2
44 1/2 - 3 = 41 1/2
The 44 3/8 lb. lobster weighed
about 41 1/2 lb more than an
average lobster.
Write examples B,
C down
B) 13/16 + 4/7
13/
16 --> 1
4/ --> 1/
7
2
1 + 1/ 2 = 1 1/2
C) 5 7/8 - 4/5
5 7/8 -->6
4/ --> 1
5
6-1=5
Write examples D and E down
Examples continue…
D) 4 2/7 • 6 9/10
4 2/7 --> 4
6 9/10 --> 7
4 • 7 = 28
E) 11 3/4 ÷ 2 1/5
11 3/4 --> 12
2 1/5 --> 2
12 ÷ 2 = 6