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In a triangle the second angle is twice the first, and the third angle is 20 degrees more than the first. Find the FIRST angle (in degrees).

Class 8Linear Equations in One VariableLinear Equations
  • A80
  • B40
  • C60
  • D45

Step-by-Step Solution

Let the first angle be . The three angles of a triangle add to 180, so → → . Check: 40 + 80 + 60 = 180. The traps 80 and 60 are the second and third angles; 45 comes from splitting 180 into four equal parts and forgetting the extra 20.
Answer: B) 40

Key idea: Translating word problems

Three steps:
1. **Pick a variable** for the unknown.
2. **Translate the words** into operations (sum, difference, product, quotient).
3. **Solve, then state the answer in the original units.**

Word clues: 'is/equals' = '='. 'sum' = +. 'difference' = −. 'product' = ×. 'quotient/per' = ÷. 'twice' = ×2. 'one more than' = +1. 'half of' = .

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