© Hamilton Trust Keeping Up Term 1 Week 2 Day 1

Objectives:• Work out, very quickly, pairs with a total of 100;• Add pairs of 2-digit numbers.

Mental Addition – Objectives

© Hamilton Trust Keeping Up Term 1 Week 2 Day 1

Mental Addition – Direct Teaching

How many more to make 100?

+3

+30

=33

Handy Hint

Look for the bond to 10 for the ones digit and the bond to 9 for the tens

digit…

© Hamilton Trust Keeping Up Term 1 Week 2 Day 1

Mental Addition – Student ActivityWith a partner, shuffle a pack of 1 to 9 digit cards.

Take it in turns to take the top 2 and use them to make a 2-digit number. Work out what is needed to make 100.

876512 439

© Hamilton Trust Keeping Up Term 1 Week 2 Day 1

Mental Addition – Direct TeachingWhat strategies could you use to solve these calculations?

65 + 31 76 + 76

74 + 19 85 + 30

57 + 68 72 + 28

© Hamilton Trust Keeping Up Term 1 Week 2 Day 1

Mental Addition – Direct TeachingPartitioning and Recombining

57 + 68

Add the 10s

50 + 60110

Add the 1s

7 + 815

Partition

Recombine 110 + 15 = 125

Mental Addition – Direct Teaching

74 + 19

Add the nearest multiple of 10 and adjust

74 93 94

+20 -1><

Simple!

© Hamilton Trust Keeping Up Term 1 Week 2 Day 1

© Hamilton Trust Keeping Up Term 1 Week 2 Day 1

Mental Addition – Individual Practice

Create pairs of 2-digit numbers using:

Add the pairs together.How many different totals can you

make?

946

or 3 285

7