Use front-end estimation to find the value of the expression. I do not understand (without adjustment)
687 - 239 (without adjustment)
is this right?
600 + 200= 800 + 126=926
If your problem is 687 - 239, it makes sense to me to do it this way:
700 = 200 = 500
Correction:
700 - 200 = 500
Right it was subtraction. So what does "without adjustment" mean?
I'm not a math teacher -- but I assume you don't need to adjust for the small differences between your estimated numbers and the actual numbers.
This site may explain it.
http://mathforum.org/library/drmath/view/65415.html
Thank you
To use front-end estimation, you can approximate each number by looking at the leftmost digit. In this case, the leftmost digit of 687 is 6, and the leftmost digit of 239 is 2.
To estimate the value of 687 - 239 without adjustment:
1. Ignore all other digits except the leftmost digit of both numbers.
2. Subtract the leftmost digit of the second number from the leftmost digit of the first number. In this case, subtracting 2 from 6 gives you 4.
3. Attach the result to the remaining digits of the first number. So, the estimated value is 400.
Therefore, the estimate for 687 - 239 is 400.