7
Review: inverse problems
Textbook: Part 1, lesson 7, pp. 16–17
GoalReview making inverse problems and splitting a number into place-value addends.
New words
inverse problem · teskari masalaplace-value addends · xona qo‘shiluvchilaritall / high · balandlow / shorter · past
Explanation
In an inverse problem the known and unknown numbers swap places. For example 27 and 51 make 78; the inverse problem: the total is 78, one part is 27, how much is the other part? We split a number into place-value addends: 24 = 20 + 4.
Worked examples
27 + 51 = 78. Inverse: 78 − 27 = 51.
An oak is 35 m and a walnut tree is 24 m. The oak is 35 − 24 = 11 m taller.
Class activity
“Inverse problem”: the teacher reads a problem and children swap the question and a known number to make a new problem. The most interesting one is written on the board.
Practice
1
35 + 24 = ?
59
2
An oak is 35 m and a walnut is 24 m. How many metres taller is the oak?
11
3
The total is 78 and one part is 27. How many in the other part?
51
4
26 = ? + ? (place-value addends)
20, 6