Math Study Guide
Estimation
Vocabulary: estimate, about, round, nearest, approximately, best guess, closest
A. Front End Estimation: Add or Subtract using only the first digit of each number.
Example
982 = 900
- 539 = 500
400
B. Rounding: Round the numbers to the given place value and add/subtract/multiply/divide.
Examples:
1. Round to the nearest hundred in
the first number and ten
in the second number.
2. 985-639=? *Round to the
^
^
nearest hundred.
1,000-600=400
429 + 16 =
^
^
400 + 20 = 420
C. Using Compatible Numbers: Compatible numbers are numbers that are close or an approximate
of the number. They are not exactly rounding, but may appear rounded.
Example:
1. Estimate the total weight of 2 boxes that weigh 9.4 pounds and 62.6 pounds
using compatible numbers.
9.4 = 10
62.6 = 63
10+63 = 73
Adding Decimals
Step 1: Line up the decimals
Step 2: Bring down the decimal.
Step 3: Add
Examples: $1.32
+0.75
$2.07
$13.22
+ 1.13
$14.35