18
Subtracting (50 − 22)
Textbook: Part 1, lesson 18, pp. 38–39
GoalLearn subtracting in parts (50 − 26 = 50 − 20 − 6).
New words
community work day · hasharseedling · ko‘chatremaining · qolganpart · bo‘lak
Explanation
We split the subtrahend into tens and ones and subtract one after the other: 50 − 26 = 50 − 20 − 6 = 30 − 6 = 24. This is the start of “subtracting a sum from a number”: 26 = 20 + 6.
Worked examples
90 − 64 = 90 − 60 − 4 = 30 − 4 = 26.
70 − 17 = 70 − 10 − 7 = 60 − 7 = 53.
Class activity
“Two steps”: children solve a sum in two steps: first subtract the tens, then the ones. Each step is shown as one jump on a number line.
Practice
1
80 − 57 = ?
23
2
50 − 23 = ?
27
3
40 poplar seedlings had to be planted. First 20, then 7 more were planted. How many are still to plant?
13
4
Of 70 seedlings, 15 are tulips, 13 are daffodils and the rest are roses. How many roses?
42