- A15 kg
- B6 2/3 kg
- C5 kg
- D8 1/3 kg
Step-by-Step Solution
Left pan = right pan: . Take 5 kg off both pans: , so kg. (Forgetting to divide by 3 gives 15 kg.)
Answer: C) 5 kg
The pans of this balance are level. Every box has the same mass, kg. What is the mass of one box?
Class 7Simple EquationsSimple Equations
Key idea: The balance principle
An equation is like a balance scale: LHS on one pan, RHS on the other, and the scale is level. Whatever you do to one side, you must do to the other to keep it balanced. So if you add 5 to LHS, add 5 to RHS. If you divide LHS by 3, divide RHS by 3.
Goal: isolate the variable on one side. Get by itself by undoing every operation around it, in reverse order, applied to BOTH sides.
Goal: isolate the variable on one side. Get by itself by undoing every operation around it, in reverse order, applied to BOTH sides.
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