9.  The length and breadth of a playground are 80 metre and 35 metre respectively.
(i) Find the cost of levelling it at Rs. 4.50 per square metre.
(ii) How long will a boy take to go three times round the field, if he walks at rate of 1.5m per second?

Hi Adarsh!!!  : )
Here Is The Answer:

Ans. (i)
Area Of Playground => Length x Breadth
                                 => 80 x 35
                                 => 2800 m²

Cost Of Levelling  1 m² => Rs. 4.50
So, Cost Of Levelling 2800 m² => 4.50 x 2800
                                                   => Rs 12600

Ans (ii)
Perimeter Of Playground => 2 ( Length + Breadth )
                                         => 2 ( 80 + 35 )
                                         => 2 ( 115 )
                                         => 230 m

Distance Travelled In Taking A Round Thrice { 3 Times } => 230 x 3
                                                                              => 690 m

Speed Of Boy => 1.5 m per second.
So, Time Taken By The Boy =>   690   => 460 seconds or 7 minutes 7 seconds { approx }.
                                                      1.5

Hope It Helps You!!!