The sum of the first 10 terms of the sequence 6, 21, 36, 51 .... is

Explanation:
The sum of the first n terms of any A.P. is given by

Sn = n/ 2[ 2a + (n - 1) × d] 

Where a is the first term and d is the common difference of the A.P,

• a = 6
• d = 15
• n = 10

S₁₀ = (10/2) × [2(6) + (10 - 1)(15)]

First, calculate inside the brackets:

2(6) = 12
(10 - 1)(15) = 9 × 15 = 135

Add the results:

12 + 135 = 147

Now, multiply by (10/2):

S₁₀ = 5 × 147 = 735

Therefore, the sum of the first 10 terms of the sequence is 735.