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In △PQR, 3∠P=4∠Q=6∠R, then find the value of (52∠P−∠Q+3∠R).
44°
30°
72°
65°
44°
Express angles as ratios by finding the LCM of coefficients (LCM of 3, 4, 6 is 12). Then, divide the LCM by each coefficient to get ratios: P:Q:R = 4:3:2. Sum of parts is 9, so 1 part is 180/9 = 20 degrees.
In triangle PQR, 3∠P = 4∠Q = 6∠R. Sum of angles in a triangle is 180 degrees.
∠P+∠Q+∠R=180°
Express angles as ratios by finding the LCM of coefficients (LCM of 3, 4, 6 is 12). Then, divide the LCM by each coefficient to get ratios: P:Q:R = 4:3:2. Sum of parts is 9, so 1 part is 180/9 = 20 degrees.
Students often treat the equality as direct values (P=3, Q=4, R=6) instead of inverse proportionality ratios.
Establish the ratio of angles
Given 3∠P=4∠Q=6∠R=k. Expressing each angle in terms of k: ∠P=k/3, ∠Q=k/4, ∠R=k/6. The ratio ∠P:∠Q:∠R is 31:41:61, which simplifies to 4:3:2.
∠P:∠Q:∠R=4:3:2
Determine individual angle values
Let the angles be 4x, 3x, and 2x. The sum of angles in a triangle is 180°, so 4x+3x+2x=180°, which means 9x=180° or x=20°. Thus, ∠P=80°, ∠Q=60°, and ∠R=40°.
x=20°
Calculate the final expression
Substitute the angles into the required expression: 52∠P−∠Q+3∠R=52(80°)−60°+3(40°). This equals \frac{160°- 60°+ 120°{5} = \frac{220°{5} = 44°.
52(80)−60+3(40)=44°
A is correct because the calculated value of the expression is 44 degrees.
This ratio technique is identical to partitioning problems in profit/loss and mixtures; remember that aA=bB=cC implies A:B:C=a1:b1:c1.