6
Review: equations and their solutions
Textbook: Part 1, lesson 6, pp. 14–15
GoalReview the rules for solving equations and the link between dm and cm.
New words
equation · tenglamaunknown · noma’lumroot (solution) · ildiz (yechim)decimetre (dm) · detsimetr (dm)
Explanation
We find the unknown with a rule: addend = sum − other addend; minuend = difference + subtrahend; subtrahend = minuend − difference. 1 dm = 10 cm, so 5 dm 4 cm = 54 cm.
Worked examples
x + 16 = 37 → x = 37 − 16 = 21. Check: 21 + 16 = 37.
98 − y = 47 → y = 98 − 47 = 51. Check: 98 − 51 = 47.
Class activity
“Equation check”: each child writes an equation and passes it to a partner. The partner solves it, puts the answer back in and says “correct” or “wrong”.
Practice
1
z − 15 = 21. z = ?
36
2
98 − y = 47. y = ?
51
3
5 dm 4 cm + 2 dm 5 cm = ? cm
79
4
12 rare birds were brought to the zoo, 3 were hawks and the rest partridges. How many partridges?
9