secrets-of-mental-math-malestrom

Answers 255
9. 104,972 10. 5,462,741
11,201
203,413
1,175,791,372
1,111,192,535,033
Guesstimates
1. 100
2.
25
2500
3. 90
4.
86
7740
7. 430
8.
310
133,300
9. 105,000
10.
11,000
1155 million
1.155 billion
Divide and Average
78
40
3120
540
17
9180
5. 310
6. 646 or
100
100
31,000
64,600
51,000
490
24,990,000
5,500,000
200,00
1100 billion
1.1 trillion
Square Root Guesstimation (page 130)
Exact (to two decimal places)
1. 4.12 2. 5.91 3. 12.76 4. 65.41 5.
17 35 163 4279
640
110
70,400
89.66
8039
1.
4.2
417
4 4.2
2
4.1
2.
5.8
635
6 5.8
2
5.9
3.
16.3 10 16.3
10163 2
13.15
4.
71
604279
60 71
2
65.5
5.
89
908039
90 89
2
89.5