Mental Math and Computational Estimation

1
Mental Math and Computational Estimation

• Mathematics Methods
• Dr. Dawn Parker

2
Calculate the Following Mentally

• 12 46 18 64
• 367 622
• 75 39
• 458 20
• 48 x 20
• 25 x 28 x 4

3
Mental Math Strategies

• Perform operation in parts
• 57 38 57 30, then 27 8
• 42 x 12 (42 x 10) (42 x 2)
• Make an easier problem
• 72 47 (72 3) (47 3)
• Drop zeros as appropriate
• 62000 4000 62 4, then add 3 zeros

4
Types of Estimation

• Measurement estimation
• To determine an approximate measure without
  making an actual measurement
• Quantity estimation
• To approximate the number of items in a
  collection
• Computational estimation
• Determine a number that is an approximation of a
  computation that we can not or do not wish to
  determine exactly

5
Suggestions for Estimation Instruction

• Find Real Examples of Estimation
• Use the Language of Estimation
• close, just about, a little less
• Connect to the Real World
• Accept a Range of Estimates and Discuss the
  Reasonableness of this Range and Why
• Focus on Flexible Methods, Not Answers
• _____________________________________
• Cautions Estimation without estimates
• Guess instead of estimate

6
Provide an Estimate for the Following

• 433 126 678 400
• 23 x 8
• 824 / 18
• 426 424 423 427
• 119 x 54
• 112 x 48 479

7
Computational Estimation Strategies

• Rounding
• Compatible Numbers
• Front End Methods
• With and Without Adjustment
• Clustering