70
Equations
Textbook: Part 2, lesson 67, pp. 56–57
GoalEquations, their roots and how to solve them.
New words
equation · tenglamaroot (the number that makes it true) · ildizunknown · noma’lumchecking the equality · tenglikni tekshirish
Explanation
An equality with an unknown number is an equation: x + 120 = 200. The value of the unknown that makes the equation true is its root. To solve an equation means to find the root: x = 200 − 120 = 80. Check: 80 + 120 = 200. In an equation with brackets, first treat the bracket as one unknown.
Worked examples
561 − (f + 154) = 137: f + 154 = 561 − 137 = 424, so f = 424 − 154 = 270.
A school bought 120 sockets, 36 of them double, the rest single: x + 36 = 120, so x = 84.
Class activity
“Balance equation”: draw scales with 120 on one pan and x and 36 on the other. Children find x to make the scales balance and check it.
Practice
1
Solve: x + 120 = 200. x = ?
80
2
Solve: 223 + (y + 178) = 742. y = ?
341
3
Solve: 561 − (f + 154) = 137. f = ?
270
4
Solve: 480 − (n − 345) = 255. n = ?
570