Question

please help me to solve this question as soon as possible please guys ​

Answer 1

Step-by-step explanation:

Method 1 : Arithmetic progression :

Sn = n/2 [2a + (n-1)d]

n = 90, a = 10, d = 1

Sn = 90/2 [2*10 + (90-1)1]

Sn = 45 * (20+89)

Sn= 45 * 109

Sn = 4905