Various Methods of Estimation
Rounding: a method by which a number is rounded up or down to the nearest
whole, tenth, etc.
For example,
3.7 becomes 4 because 3.7 is closer to 4 than 3. Then multiplied 4 by 4 jugs
to get about 16 liters.
·
0-4 stay with the same whole number.
·
5-9 round up to the next whole number.
Front-end estimation: a method by keeping the first digit of the number and
changing all the other digits to zero.
For example,
for 3.7 we keep the 3 and drop the 0.7. So our estimate would
look like this: 3x4 is about 12 liters.
·Keep the first digit and change all the other digits to zero.
o Example: 546 becomes 500, 699 becomes 600
o Can combine with other estimation strategies.
Compatible numbers: a method of using friendly or nice numbers that can be
easily calculated mentally.
For example,
2.5 x 4 can become 3, 2, or 2.5 depending on which number you prefer
to work with.
o 3x4= 12
o 2x4 = 8
o 2.5x4 =10
Compensation: a method of adjusting a computational estimate to make it
closer to the calculated answer.
For example,
2.629 x 4. Think 2x4= 8 (front end estimation) then 0.629 is
about 0.5x 4=2, then add 8+2=10.
2.629
X 4
2x4=8
Estimate 0.629 as 0.5
0.5x4 = 2
8+2=10 this is your estimate!!
· A method of adjusting your estimate to make it closer to the
calculated answer.