2
Review: tens and ones within 100
Textbook: Part 1, lesson 2, pp. 6–7
GoalReview numbers within 100 as tens and ones; adding and subtracting whole tens.
New words
ten · o‘nlikone (unit) · birliknumber line · sonlar nuriround number (whole tens) · yaxlit son
Explanation
A two-digit number is made of tens and ones: 5 tens 6 ones = 56. When we add whole tens we just add the tens: 4 tens + 3 tens = 7 tens, so 40 + 30 = 70.
Worked examples
72 = 7 tens 2 ones; 100 = 10 tens.
40 + 50 − 20: first 40 + 50 = 90, then 90 − 20 = 70.
Class activity
“Number line”: a tape marked with tens from 0 to 100 is laid on the floor. A child starts at 30 and jumps by commands such as “+ 40”, “− 20”; the class says the answer aloud.
Practice
1
3 tens 7 ones = ?
37
2
72 = ? tens ? ones
7, 2
3
40 + 50 − 20 = ?
70
4
One row has 30 tomato seedlings and the second has 40. How many in all?
70