Question

the length and breadth of a rectangular field are in the ratio of 5:4 and its area is 3380 square mt find the cost of fencing it at the rate of rs 75 per mt

Answer 1

let the length be 5x & b=4x
now 5x*4x= 3380
20x²=3380
x²=169
x=13
l=5*13=65
b=4*13=52
Perimeter=2(l+b)
=2(65+52)
=234
cost of fencing=234*75
=rs 17550

Answer 2

Let the length of field be 5x
and the breadth be 4x

ATQ,

$area = l \times b \\ = > 3380 = 5x \: \times \: 4x \\ = > 3380 = 20 {x}^{2} \\ = > {x}^{2} = \frac{3380}{20} \\ = > {x}^{2} = 169 \\ = > x = \sqrt{169} \\ = > x = 13$
Now, Length= 5x= 5×13=65m
Breadth=4x=4×13=52cm

Perimeter=2(l+b)
=2(65+52)
= 234m

Now, cost of fencing= perimeter × rate
= 234 × 75
= Rs 17,550

Hope you understood.
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