Approaches and methodologies
 

Front-end strategy

This strategy has its strongest application in addition. The left-most digits (front-end) are the most significant in forming an initial estimate and can be used on their own in the earlier stages to establish a rough estimate:


1.54
6.35
0.99
2.51 +
front-end process:

Add the front-end amounts: €1 + €6 + €2 = €9, adjust by grouping the cent to form euro 54c + 35c makes €1 approx. 99c is nearly €1 and 51c is nearly 50c cents estimate: €2.50 overall estimate is €11.50 (€9 + €2.50).

This strategy can be introduced by using money initially but works equally well with whole numbers, fractions and decimals. The adjustment stage can be introduced gradually as the children become familiar with the concept of ‘nearly €1′ or ‘nearly 50c’. It can also be accomplished with multiplication for example,

369 x 6
300 x 6 = 1800
70 x 6 = 420 Estimate is 2220