Aptitude - Area - Discussion

Discussion Forum : Area - General Questions (Q.No. 1)
1.
The ratio between the length and the breadth of a rectangular park is 3 : 2. If a man cycling along the boundary of the park at the speed of 12 km/hr completes one round in 8 minutes, then the area of the park (in sq. m) is:
15360
153600
30720
307200
Answer: Option
Explanation:

Perimeter = Distance covered in 8 min. = 12000 x 8 m = 1600 m.
60

Let length = 3x metres and breadth = 2x metres.

Then, 2(3x + 2x) = 1600 or x = 160.

Length = 480 m and Breadth = 320 m.

Area = (480 x 320) m2 = 153600 m2.

Discussion:
48 comments Page 1 of 5.

Ekta said:   3 years ago
Distance = Speed * time.

To convert km/hr to m/sec, multiply 5/18.

So, Dist= 12* 5/18 * 8 * 60 ( since, 1 min = 60 sec so 8*60),
= 1600 m.
(20)

Merv zoro said:   3 years ago
l/b = 3/2.
s = d/t.

12 x 8/60 = 1.6km,
2(l+b) = 1.6
2(3b/2+b) = 16,
2(5b/2) = 1.6,
b = 1.6/5.
b = 0.32
l = 0.48.

lxb = 0.153km2.
a = 0.1536x10^(6),
a = 153600 m2.
(11)

Apurv said:   4 years ago
Why taking x in common both length and Breadth. Why can't be we take as length = x and breadth = y? Please anyone explain.
(7)

Hema M said:   6 years ago
1 km /hr = 1000/3600 m/s,
= 5/18 m/s.
(6)

Hema M said:   6 years ago
Length =3x and Breadth = 2x.

Distance = 12000/60 = 200 * 8 = 1600,
3x+2x=1600,
5x^2=1600,
x^2=1600/5=320,
x=160.

3x = 3 * 160 = 480 and 2x = 2 * 160 = 320.

Area = (480*320)m^2.
= 153600 m^2.
(6)

Subrata Mondal said:   4 years ago
Thank you so much for this explanation and this season is very helpful.
(4)

Hema M said:   6 years ago
1 km = 1000 m.

Then, distance=speed*time,
Here speed is 12 km/hr.
12 km is converted to 12*1000 m.
Then, 8 mins is converted to 8/60 sec.
So, 12*1000 * 8/60 = 1600 m.
(3)

Riya said:   7 years ago
Even 1 hour is converted to minutes only not to seconds. Why?

If we are converting km to metres then hours and minutes should be converted to seconds only.

Right?
(2)

Riya said:   7 years ago
Why 8 minutes not converted to seconds. If it is converted to seconds then we should use 480, but here they used 8 to multiply. Why?

Please anyone explain.
(2)

Mahendra chozhan said:   10 years ago
@Fijo.

We can use but you have to convert the given time also into seconds, (i.e) 8 mins to 8*60 = 480 sec. Since it is given as 8 mins and 12 km/hr, we are converting them into 12*1000 = 12000 m and 1 hr = 60 mins.

Now the formula to find the distance is Speed = Distance/Time.

Hence Distance = Speed*Time.

D = 12000/60*8 = 200*8 = 1600 m.

Let x be some value.

The ratios given are 3: 2, (i.e) length will be 3 times the 'x' value and the breadth will be 2 times the 'x' value.

The formula for perimeter is 2(l+b).

l = 3*x.
b = 2*x.

(i.e) 2(3x+2x) = 1600 which is already found is already found.

6x+ 4x = 1600.
10x = 1600.
x = 160.

Now substitute value of x in length.

(i.e) 3x = 3*160 = 480 m.

Substitute value of x in breadth.

(i.e) 2x = 2*x = 2*160 = 320.

Therefore we have length and breadth.

Hence area of a rectangle is l*b = 480*360 = 153600 meters is the answer.
(2)


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