Subtraction Written Methods Written Methods Throughout their years

Subtraction Written Methods

Written Methods • Throughout their years at school, children should progress from informal jottings, practical taking away and number line methods to formal efficient written methods. • By the end of Year 3, children should be confident using short efficient written methods for all four operations + - x ÷ • Children become secure with these methods with regular practice and should be able to apply skills to problem solving.

Blank Number Line • An empty number line helps children to count back and forward to subtract amounts. Children begin jumping back and progress onto complimentary addition to count forward to find differences. • Counting back 45 – 22 20 + 2 • Complimentary Addition 45 - 22 -2 23 - 20 25 45 8 + 10 + 5 = 23 +8 + 10 +5 22 30 40 45

Your Turn! • Can you use complimentary addition on a blank number line to solve these additions? • 43 - 25 = • 51 - 36 = • 124 - 43 = Remember! Start on the smallest no. and jump to the largest

Expanded Method • Expanded method is completed in preparation for the short efficient written method. This method is supported by apparatus such as diennes rods, place value counters and straws. 47 - 23 40 + 7 T U 2 4 20 + 3 40+7 - 20+3 20+4 = 24

Expanded Method • Expanded method extend to demonstrate the process of exchanging. This is where a ten is swapped for ten ones/units. 4 7 - 29 40 + 7 30 T U 1 8 20 + 9 17 40+7 - 20+9 10+8 = 18

Your Turn! • Can you use the expanded method to solve these subtractions? • 36 - 22 = • 45 - 36 = • 166 - 23 =

Column Subtraction • Expanded method leads onto a compact efficient written method. With this method children need to be confident with place value to exchange between hundreds ad tens. TU 45 - 23 22 TU 4 1 53 - 25 28 HTU 1 12 1 234 - 56 178

Column Subtraction • Rules of column subtraction: – Start with the biggest number – Align the columns H T U – Subtract from the units first – Exchange tens for units, exchange hundreds for tens TU 42 -25= -

Column Subtraction • Once children are confident using the compact method of column subtraction for whole numbers, it progresses on to decimal amounts with money. £ 1. 45 - 28 p 3 1 £ 1. 45. 28 £ 1. 17 £ 5. 00 - £ 1. 35 4 9 1 1 £ 5. 00 - £ 1. 35 £ 3. 65

Your Turn! • Can you use the column method to solve these subtractions? • 37 -45= • 232 -36= • £ 5. 00 -37 p=