RRB NTPC · Question 10
A piece of cloth costs Rs. 35. If the piece were 4 m more longer and each meter was to cost Rs. 1 lesser, then the total cost would remain unchanged. How long is the piece of cloth? A. 10 m B. 14 m C. 12 m D. 8 m
Show answer & explanation
Answer: (D) A
Explanation
Let the length be x m, so the price per metre is 35/x. Then (x + 4)(35/x − 1) = 35. Expanding: 35 − x + 140/x − 4 = 35, so x² + 4x − 140 = 0, i.e. (x + 14)(x − 10) = 0. The length is 10 m (check: Rs 3.50/m; 14 m at Rs 2.50 = Rs 35).