ICSE & CBSE Board Question Based on Arithmetic Progression of RS Aggarwal

Here you have to find the

(i) sum of all odd numbers

(ii) Between two numbers which is given

This is the Question Number 14 Of Exercise 11 C of RS Aggarwal Solution.

Deepak BoraNewbie

# Find the sum of all odd numbers between 0 and 50.

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Let,

sum = 1 + 3 + 5 + 7 + ……+49.

this is an A.P, whose first term(a) = 1 and last term(Tn) = 49.

common difference(d) = 3-1 = 2

Total no. of odd number lie b/w 0 and 50 = n

but,

Tn = a + (n-1)d

or, 49 = 1 + (n-1)2

or, n-1 = 48/2 =24

n = 25

hence

sum = n/2(a + Tn)

sum = 25(1 + 49)/2

sum = 25×50/2 = 25×25

sum = 625