How many terms of Arithmetic Progression (A.P) 21, 18, 15, 12 , ..... must by taken to give the sum zero?
A
10
B
15
C
22
D
27
Correct Answer: 15
ATQ, 5x + 6x + 7x = 180 Or, 18x = 180 Or, x = 10 So, the difference in degrees between the biggest and the smallest angles = 70 - 50 = 20 degree.