Download Estimating Products

Name
_
Reteaching
8-2
Estimating Products
£
f
M
-
.
for
q
When you are working with fractions and mixed numbers, you can estimate using
rounding, compatible numbers, or compatible benchmark fractions.
lo
Estimate
x 12 using a compatible
benchmark fraction.
Estimate 130 X 21 using a whole number
that is compatible with the denominator.
130
w
Change 21 to the nearest
whole number that is
compatible with 10.
x 21
w
130
w
10
w
1 x 12 = 3
?o x 20 = 6
~ x 21 ~ 6
lo
1
x 12
4
Think: 20 .;..10
3 x 2
=
=
~10 x 12 ~ 3
2.
Round
to a compatible
benchmark fraction. Since
is
close to and 4 is a factor of
twelve, use
lo
1-
Think: 12 -;-4 = 3.
1 x 3 = 3.
6.
ffif61?
U!!
Estimate each product by using compatible numbers or benchmark fractions.
19 =
1. 1x
6
4. 31 x 25
2.
=
1x 10 =
3.
7
5. Lx
12
8
x 90
6. JL
16
18 =
=
4_
8. 35 x~=
12
7. 43 x 27 =
Q x 23 =
9. 16 x 9-
Estimate each product by rounding each factor to the nearest whole number.
10. 6~ x
5i -7 Round 6~:'
Round
5i:
Multiply:
_
6
11. 102x4Q
13. 4~ x 21 =
=
96----
_
14. Reasonableness Carlotta estimated that ~ x 20 is about ~ x 14 = 6. Is her estimate
reasonable? Why or why not?
15. Critical Thinking Why are the estimates of 160 x 18 shown below different? Is one
estimate better than the other?
.e.
x
10
24
18 ~ ..§... x 20 = 12
Topic 8
10
160 x
18"" -21 x 18 = 9.
16. Show three ways to estimate
lx
5lldentify
each method you use.
17. Explain It Mr. Simpson lives 11130 miles from his office. He estimates that he
commutes 11 x 2 x 5, or 110 miles each week. Is his estimate an overestimate or an
underestimate? Explain.
18. Which benchmark fraction could you use to estimate the product of 38
x
l2 ?
19. Geometry Which is the best estimate for the area of a square with sides equal to
inches?
A
_
3i-
3 sq in.
S 6 sq in.
C 9 sq in.
D 16 sq in.
20. Joyce and Marianne have money jars. Joyce has 54 dimes in her jar. Marianne has 190
as many dimes as Joyce. Estimate the number of dimes that Marianne has in her jar.
A
co
jj
~g
o
~c
60 dimes
S 45 dimes
C 6 dimes
D 5 dimes
g
1;
'"
D@
Topic 8
25