The sum of first five multiples of 3 is
a. 45
b. 55
c. 65
d. 75
Solution:
An arithmetic progression (AP) is a sequence where the two consecutive terms have the same common difference. It is obtained by adding the same fixed number to its previous term.
From the question,
The first five multiples of 3 are 3, 6, 9,12 and 15.
First term, a = 3,
common difference, d = 6 - 3 = 3 and
number of terms, n = 5
The formula to find the sum is
Sₙ = n/2 [2a + (n - 1)d.
Substituting the values
S₅ = 5/2 [2a + (5 - 1)d]
S₅ = 5/2 [2 × 3 + 4 × 3]
So we get
S₅ = 5/2 (6 + 12)
S₅ = 5 × 9
S₅ = 45.
Therefore, S₅ = 45.
✦ Try This: Find the sum of the first 30 multiples of 4
☛ Also Check: NCERT Solutions for Class 10 Maths Chapter 5
NCERT Exemplar Class 10 Maths Exercise 5.1 Problem 18
The sum of first five multiples of 3 is, a. 45, b. 55, c. 65, d. 75
Summary:
An arithmetic progression (AP) is a sequence where the two consecutive terms have the same common difference. The sum of the first five multiples of 3 is 45
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