3
Past 100 on the 120 chart
Discover Mathematics P2: Term 1, Lessons 11–20
GoalCount, add and subtract on the 120 chart, going past 100.
New words
120 chart · a chart with the numbers 1 to 120 in rows of tenone hundred · ten tens, the number 100row · numbers side by side from left to right
Explanation
The 120 chart goes past 100. After 100 come 101, 102, 103 and so on. The last two rows are 101 to 110 and 111 to 120. To add, move to the right or down one row for ten more. To subtract, move left or up. So 100 + 7 = 107 and 116 − 10 = 106.
Worked examples
100 + 7: start at 100 and count on 7 to 107.
106 + 10: move down one row from 106 to 116. 106 + 10 = 116.
118 − 10: move up one row from 118 to 108. 118 − 10 = 108.
Class activity
Play 101 and over. Take turns to say the next number from 101, counting 1, 2 or 3 numbers each time. The player who says 120 wins. Use a chart to check.
Practice
1
What number is 3 more than 100?
103
2
What number comes after 109?
110
3
What is 105 + 10?
115
4
What is 120 − 10?
110
5
Find the missing number: 114, 115, ?, 117.
116