NumericalModerate3 marks
The following numbers, k + 3, k + 2, 3k – 7 and 2k – 3 are in proportion. Find k.
Topic: Ratio and proportion
Previous-year question practice database
Answer
Solution diagram
Exam answer
(k+3)/(k+2) = (3k−7)/(2k−3).
(k+3)(2k−3) = (k+2)(3k−7).
2k²+3k−9 = 3k²−k−14.
k²−4k−5=0.
(k−5)(k+1)=0.
Answer: k=5 or −1.
Explanation
For numbers in proportion, cross-products are equal. Solve the resulting quadratic equation.
More from Ratio and Proportion (Including Properties and Uses)
(x + 3), 1, (3x − 7) and −5 are in proportion. The value of x is :2026Using properties of proportion, find the value of 'x':
(6x² + 3x - 5) / (3x - 5) = (9x² + 2x + 5) / (2x + 5) ; x ≠ 02025The given table shows the distance covered and the time taken by a train moving at a uniform speed along a straight track.
The values of x and y are :2024find (a + b) / (a - b)2024Hence using properties of proportion, find a : b.2024The mean proportional between 4 and 9 is :2023