How many rows did a farmer make for planting trees if he planted 4 more trees in each row than the number of rows, and planted 221 trees in total? Let the number of rows be \(x\), and the number of trees in each row be \(x+4\).
Answer and explanation
Correct answer: 13
The total number of trees gives the equation \(x(x+4)=221\). Thus, \(x^2+4x-221=0\), which factors as \((x-13)(x+17)=0\). Hence, \(x=13\) or \(x=-17\), but the number of rows cannot be negative, so the correct answer is 13. Exam tip: In word problems, check the roots against the given context and reject impossible negative values.
Frequently asked questions
What is the correct answer to this question?
13
Why is this the correct answer?
The total number of trees gives the equation \(x(x+4)=221\). Thus, \(x^2+4x-221=0\), which factors as \((x-13)(x+17)=0\). Hence, \(x=13\) or \(x=-17\), but the number of rows cannot be negative, so the correct answer is 13. Exam tip: In word problems, check the roots against the given context and reject impossible negative values.
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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