Question 2
- Represent the following situations in the form of quadratic equations :
(i) The area of a rectangular plot is . The length of the plot (in metres) is one more than twice its breadth. We need to find the length and breadth of the plot.
(ii) The product of two consecutive positive integers is 306. We need to find the integers.
(iii) Rohan's mother is 26 years older than him. The product of their ages (in years) 3 years from now will be 360. We would like to find Rohan's present age.
(iv) A train travels a distance of 480 km at a uniform speed. If the speed had been 8 km/h less, then it would have taken 3 hours more to cover the same distance. We need to find the speed of the train.
Let's represent each situation as a quadratic equation.
Step 1 — Rectangular Plot Dimensions
We need to find the length and breadth of the plot. Let the breadth of the rectangular plot be metres. The length is one more than twice its breadth. So, the length is metres. The area of the plot is given as . The area of a rectangle is length multiplied by breadth.
Let's expand the left side.
Now, we move all terms to one side to form a quadratic equation.
This equation represents the situation for the rectangular plot.
Step 2 — Consecutive Integers Product
We need to find two consecutive positive integers. Let the first positive integer be . Since they are consecutive, the next integer will be . Their product is given as 306.
Let's expand the left side of the equation.
Now, we move 306 to the left side to get the standard quadratic form.
This equation represents the situation for the consecutive integers.
Step 3 — Rohan's Age
We need to find Rohan's present age. Let Rohan's present age be years. Rohan's mother is 26 years older than him. So, his mother's present age is years. We consider their ages 3 years from now. Rohan's age after 3 years will be years. His mother's age after 3 years will be , which is years. The product of their ages 3 years from now will be 360.
Let's expand the left side using the distributive property.
Combine the like terms.
Now, we move 360 to the left side to form the quadratic equation.
This equation represents the situation for Rohan's age.
Step 4 — Train Speed
We need to find the speed of the train. Let the uniform speed of the train be . The distance traveled is 480 km. The time taken to cover this distance is .
If the speed had been 8 km/h less, the new speed would be . The new time taken would be . This new time is 3 hours more than the original time.
Let's rearrange the equation to isolate the terms with .
Now, we find a common denominator for the left side.
Let's expand the numerator and the denominator.
Simplify the numerator.
Multiply both sides by .
Finally, move all terms to one side to form the quadratic equation.
This equation represents the situation for the train's speed.
Answer
(i) The length and breadth of the plot satisfy the equation . (ii) The two consecutive positive integers satisfy the quadratic equation . (iii) Rohan's present age satisfies the quadratic equation . (iv) The speed of the train satisfies the quadratic equation .
More questions in Exercise 4.1
- Check whether the following are quadratic equations :
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
(viii)
- Represent the following situations in the form of quadratic equations :
(i) The area of a rectangular plot is . The length of the plot (in metres) is one more than twice its breadth. We need to find the length and breadth of the plot.
(ii) The product of two consecutive positive integers is 306. We need to find the integers.
(iii) Rohan's mother is 26 years older than him. The product of their ages (in years) 3 years from now will be 360. We would like to find Rohan's present age.
(iv) A train travels a distance of 480 km at a uniform speed. If the speed had been 8 km/h less, then it would have taken 3 hours more to cover the same distance. We need to find the speed of the train.