Fundamentals of Mathematics, 2008a

481
8.2.2.10 Practice Set E
Exercise 8.2.13 (Solution on p. 505.)
Estimate the sum: 61.02 + 26.8.
Exercise 8.2.14 (Solution on p. 505.)
Estimate the sum: 109.12 + 137.88.
8.2.2.11 Sample Set F
Example 8.8
Estimate the product: (31.28) (14.2).
Notice that 31.28 is close to 30,
}{{}
one nonzero
digit
and that 14.2 is close to 15.
}{{}
two nonzero
digits
The product can be estimated by 30 · 15 = 450. ( 3 · 15 = 45, then ax one zero.)
Thus, (31.28) (14.2) is about 450. In fact, (31.28) (14.2) = 444.176.
Example 8.9
Estimate 21% of 5.42.
Notice that 21% = .21 as a decimal, and that .21 is close to .2.
}{{}
one nonzero
digit
Notice also that 5.42 is close to 5.
}{{}
one nonzero
digit
Then, 21% of 5.42 can be estimated by (.2) (5) = 1.
Thus, 21% of 5.42 is about 1. In fact, 21% of 5.42 is 1.1382.
8.2.2.12 Practice Set F
Exercise 8.2.15 (Solution on p. 505.)
Estimate the product: (47.8) (21.1).
Exercise 8.2.16 (Solution on p. 505.)
Estimate 32% of 14.88.
8.2.3 Exercises
Estimate each calculation using the method of rounding. After you have made an estimate, nd the exact
value and compare this to the estimated result to see if your estimated value is reasonable. Results may
vary.
Exercise 8.2.17 (Solution on p. 505.)
1, 402 + 2, 198
Exercise 8.2.18
3,481 + 4,216
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