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The three sides of a triangular park measure m, m and m, and its perimeter is 60 m. How long is the shortest side?

Class 7Simple EquationsSimple Equations
  • A20 m
  • B21 m
  • C24 m
  • D15 m

Step-by-Step Solution

Perimeter = → → . The sides are 15 m, 21 m and 24 m, and 15 + 21 + 24 = 60 ✓. The shortest side is itself, 15 m; 21 m and 24 m are the other two sides; 20 m comes from dividing 60 by 3 as though all three sides were equal.
Answer: D) 15 m

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.

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