Question

30+60+90+..........+450 find sum of these​

Answer 1

Answer:

Given numbers are in A. P.

here first term = 30

common difference, d = 60 - 30

= 30

last term = 450

sum of the numbers = n/2(a + l)

n = ?

let an = 450

=> a + (n - 1 ) d = 450

=> 30 + (n - 1 ) 30 = 450

=> 30 + 30n - 30 = 450

=> 30n = 450

=> n = 450/30

=> n = 15

hence sum of the numbers = 15/2 (30 + 450)

= 15/2(480)

= 15(240)

= 3600

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