Question

In the middle of a round-about of radius 22 m, there is a circular tank of radius 8 m. Find the cost of turfing the remaining portion at the rate of 6 per sq metre.


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Answer 1

Answer:

Rs.7290

Explanation:

Given,

• round-about which has the radius (R) of 22m
• the circular tank which has a radius (r) of 8m

Now,

The area of the remaining portion is given by,

$\rm = \pi ({R}^{2} - {r}^{2} )$

$\rm = \dfrac{22}{7} \{ {(22)}^{2} - {(8)}^{2} \}$

$\rm = \dfrac{22}{7} \{ 484 - 64 \}$

$\rm = \dfrac{22}{7} \{ 420 \}$

$\rm = \dfrac{22}{7} \times 420$

$\rm = 22 \times 60$

$\rm = 1320 {m}^{2}$

∴ Total cost of turfing remaining portion is:-

= Remaining portion × rate of turfing

• rate of turfing = Rs.6/- per m² (given)

= 1320 × 6

= 7920

∴ Hence, cost of turfing the remaining portion is Rs.7920

_______________________________

Answer 2

Answer:

Correct option is A)

Length of rectangle =90m

Breadth of rectangle =32m

Area of rectangular ground =90m×32m=2880m

2

Radius of circular tank =14m

Area enclosed by circular tank in the ground

πr

2

=

7

22

×14×14=616m

2

∴ Area left for turfing =(2880−616)m

2

=2264m

2

Cost turfing 1m

2

area =Rs.2.50

∴ Cost of turfing 2264m

2

area

=Rs.2.50×2264

=Rs.5660