Question

find the sum of first 40 odd numbe

Answer 1

Hey!!
Here is the answer ..

The odd number series is..
1 ,3, 5, 7 ,9......, 77, 79.

Common difference--> 2
(a) first number --> 1
Total number of terms --> 40

The given series is in A. P

Sum = n/2 x (a + Tn)
= 40/2 x (1 + 79)

= (40 x 80)/ 2

= 3200/2

= 1600

Hence,
1 + 3 + 5 + 7 + 9 + .  .  .  .   + 79 = 1600

Sum of first 40 odd numbers is 1600.

This is the answer.
I hope it helps you.

Answer 2

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step 1

Address the formula, input parameters & values.

Input parameters & values:

The number series 1, 3, 5, 7, 9, . . . . , 79.

The first term a = 1

The common difference d = 2

Total number of terms n = 40

step 2

apply the input parameter values in the AP formula

Sum = n/2 x (a + Tn)

= 40/2 x (1 + 79)

= (40 x 80)/ 2

= 3200/2

1 + 3 + 5 + 7 + 9 + . . . . + 79 = 1600

Therefore, 1600 is the sum of first 40 odd numbers.

Thanks