Course Guide - USAID Teacher Education Project

Unit 1 Number and OperationsWeek 3, Session 2: Introduction to Decimals2. Maths Concepts to be studieda. Decimals are a way to write fractions using a numeral’s position in base-10 place value.When working with whole numbers, students saw that each numeral increased by amagnitude of ten moving to the left, and decreased by a magnitude of 10 moving to theright. A number such as 23 could be written with a decimal point as 23.0 withoutchanging its value.b. Students need to develop “decimal sense” to understand how decimals are named andthe quantity they represent. One way to address this is to work with a number line thatgoes from 0.0 to 1.0 with points in between indicating tenths.c. A second way is to use a 10 x 10 blank grid where a full row or column colored inindicates tenths. It is important that students understand how this grid is different fromthe Hundred Chart. In the Hundred Chart each cell was worth “1” and the “whole” wasworth 100.In the case of the decimal grid, each grid is only one unit, and each cell is 1/100 of thewhole. Thus two decimal grids would be worth 2.0, but two small squares colored inwould be worth 0.02.d. Comparing and Ordering Decimals: Placing a group of decimal numbers in order is achallenging task for children. Consider: 6.6, 6.7, 6.08, 6.55, and 6.551. All five ofthese numbers have a six in the units place. But some are “shorter” numbers with onlytwo digits while some are “longer numbers” with up to four digits. All of which givesrise to confusion (see below regarding how children think of these).e. Fraction-Decimal Equivalents: Decimals, as mentioned before, are used as analternative to the a/b model for writing fractions. As such, every fraction has its decimalequivalent, which is either truncated after several places (such 1/8’s equivalent 0.125)