A person travels a distance of 1125 km in x hours at a speed of x+20 km/h. What is the value of x?
Answer and explanation
Correct answer: 25 hours
Using distance = speed × time, we get x(x+20)=1125, or x²+20x−1125=0. Factoring gives (x−25)(x+45)=0, so x=25 or x=−45. Since time cannot be negative, x=25 hours is the valid answer. Exam tip: In speed–distance–time problems, first write distance = speed × time and reject any negative time root.
Frequently asked questions
What is the correct answer to this question?
25 hours
Why is this the correct answer?
Using distance = speed × time, we get x(x+20)=1125, or x²+20x−1125=0. Factoring gives (x−25)(x+45)=0, so x=25 or x=−45. Since time cannot be negative, x=25 hours is the valid answer. Exam tip: In speed–distance–time problems, first write distance = speed × time and reject any negative time root.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Quadratic Equations. Topic: Word Problems and Applications.
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