Aptitude - Area - Discussion
Discussion Forum : Area - General Questions (Q.No. 5)
5.
A rectangular park 60 m long and 40 m wide has two concrete crossroads running in the middle of the park and rest of the park has been used as a lawn. If the area of the lawn is 2109 sq. m, then what is the width of the road?
Answer: Option
Explanation:
Area of the park = (60 x 40) m2 = 2400 m2.
Area of the lawn = 2109 m2.
Area of the crossroads = (2400 - 2109) m2 = 291 m2.
Let the width of the road be x metres. Then,
60x + 40x - x2 = 291
x2 - 100x + 291 = 0
(x - 97)(x - 3) = 0
x = 3.
Video Explanation: https://youtu.be/R3CtrAKGxkc
Discussion:
75 comments Page 1 of 8.
Sai said:
1 decade ago
What is the need of 60x + 40X -pow (x, 2) ?
Lekshmi said:
1 decade ago
Same doubt as sai said above,
60x + 40x - x2 = 291?
60x+40x?
60x + 40x - x2 = 291?
60x+40x?
Prajwal said:
1 decade ago
I got it. Its because. 60 and 40 get multiplies to width and. Since there are two cross roads. There will be a common space for two roads. (width of two cross roads is width^2).
Shreya said:
1 decade ago
My doubt is
60x+40x-x2=291?.
60x+40x-x2=291?.
Tanya said:
1 decade ago
Its because the area of 2 roads has come out to be 291m2. Rest of the explaination has been given by prajwal.
Naju said:
1 decade ago
Draw the figure you can c two cross road intersect, so we need to subtract it.
Ayoosh said:
1 decade ago
For all having probs in the 60x + 40x - x^2!!!!
See road is a rect. and they are intercrossing. let the width be x, then for one road area will be 40x and for the other road will be 60x since 60 and 40 will be the lengths of road.
now, we area of roads is 291 m2, so
ar(road1) + ar(road2) - ar(intercrossing)
60x + 40x - x^2 = 291 and then on you can find the ans
See road is a rect. and they are intercrossing. let the width be x, then for one road area will be 40x and for the other road will be 60x since 60 and 40 will be the lengths of road.
now, we area of roads is 291 m2, so
ar(road1) + ar(road2) - ar(intercrossing)
60x + 40x - x^2 = 291 and then on you can find the ans
(9)
Jhola said:
1 decade ago
Very good ayoosh.
Ayoosh said:
1 decade ago
If we dont subtract the X^2 THEN the area of intercrossing will be doubled since its accountd in area of both roads !! thats why we subtract x^2
(2)
Sujay ramesh said:
1 decade ago
Thanks ayoosh. Your explanation is good :).
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