Distance vs. Time

TIMS Bit

Answers will vary but should include students' strategies. Sharing these strategies with the class, or in groups, will allow students to see several ways of making estimates.

1. 10 is an example of a good estimate. 14 × 10 = 140
2. 10, 11, or 12. 25 × 10 = 250;
   25 × 11 is the same as 25 + 10 = 25 or 275;
   Alternatively, there are four 25s in 100 and there are almost three 100s, so there are about, or slightly less than, twelve 25s.
3. 20 × 20 = 400 which is too high; 20 × 10 = 200 which is too low; 15 is an example of a good estimate.
4. 40 × 60 is 2400 and 40 × 70 is 2800; 65 is a good estimate.