Distance walked in three weeks = (21*150)/1000 km

= 3.15 Km

Area of rectangle = 225/3 = 75 sq.cm

Breadth of rectangle = Area/Length  =  75/15  = 5 cm

Side of the square = square root(Area) = square root(225)  = 15 cm

Required difference = 15 - 5 = 10 cm.

x + x+2 + x+4 + x+6 = 4 * 24

=> 4x + 12 = 96

=> 4x = 96 - 12 = 84 

x = 84/4 = 21

B = 21 + 2 = 23

D = x + 6= 21 + 6 = 27

B * D = 23 * 27 = 621

Distance covered by truck in 12 hours = speed * time

= 70 * 12 = 840 km

Distance covered by car in 12 hours = 840 + 120 = 960 km

Average speed of car = Distance covered/ time taken

= 960/12 = 80kmph

Required average = (125 + 336 + 334 + 486 + 564 + 625 + 702 + 800 )/8 = 3872/8  =  484

The word BELIEVE consist of 7 letters in which E comes thrice

Required number of arrangements  =  (7 * 6 * 5 * 4 * 3 * 2 * 1 )/ (3 * 2 * 1 )       =  840

Speed of train = Length of train/Time taken in crossing the pole   = 420 /75 = 6 m /sec

Interest/Principal  = 162/100

Rate = (Interest/Principal)  * (100/Time)

= (162/100) * (100/9) = 18 % per annum

Required time

= LCM (10, 6 and 14)

= 210 seconds

= 3 minutes 30 seconds

C.I = P[(1 + R/100)^T - 1]
=>3041.28 = P[(1 + 16/100)^T - 1]
=> 3041.28 = P[(29/25)² - 1]
=> 3041.28 = P[841/625 - 1]
=> 3041.28 = P[216/625]
=> P = 3041.28 * 625/216
P = 8800