Equations: the rule for the unknown component
Compose an equation from a story, solve it with the rule for the unknown component and check by substitution. Section: Grades 3-4, equations with an unknown component; formulas and the root of an equation for Grades 5-7 are in another studio.
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الدليل
A studio for Ukrainian grades 3-4 (НУШ textbooks, part 1, equations). The book writes the unknown as x and solves by the rule for the unknown component (unknown addend = sum − known addend, unknown minuend = difference + subtrahend, and so on). The root is checked by substitution.
Three tasks here are word problems. First compose the equation: place the numbers, a sign and x, then find x. The fourth task is an inequality with a variable, x + 37 < 61. In grades 3-4 it is solved by trying numbers one by one.
Equalities have properties: adding or subtracting the same number on both sides keeps the equality. This is in the lesson.
The «why?» question asks how to check the answer.