58
Round tens
Textbook Part 2, pp. 36–37
GoalRead and write the round tens 10, 20, … 100; add and subtract whole tens.
New words
round number (whole tens) · yaxlit soncounting in tens · o‘ntalab sanashhundred · yuz
Explanation
Two-digit numbers ending in zero are round numbers: 10, 20, 30, 40, 50, 60, 70, 80, 90. Ten tens make 100. We add tens just like ones: 2 tens + 3 tens = 5 tens, so 20 + 30 = 50.
Worked examples
Their Uzbek names: o‘n, yigirma, o‘ttiz, qirq, ellik, oltmish, yetmish, sakson, to‘qson, yuz (10 … 100).
Ballpoint pens have been used for 80 years; the erasable pen was invented 40 years later: 80 − 40 = 40 years ago.
Class activity
Children pass round ten-bundles, counting in tens: “ten, twenty, thirty…” — each child adds one bundle.
Practice
1
30 + 40 = ?
70
2
90 − 50 = ?
40
3
How many tens are in 60?
6
4
Write the missing numbers: 10, 20, _, 40, _, 60
30, 50