8th Grade · The Number System
Rational Approximation
8.NS.A.2
Definition
A rational number (fraction or decimal) used to estimate an irrational number. Found by squeezing the value between closer and closer rational bounds.
Examples
- √2 is between 1 and 2, then between 1.4 and 1.5, narrowing to about 1.41.
- Square the guess, compare to the target, then narrow the range one decimal place at a time.
Key rule
Squeeze the irrational number between closer and closer rational bounds.
Memory hook
Get closer and closer with decimals.