Question

Find the sum of the first 7 multiples of 13.

Answer 1

Answer:

Step-by-step explanation: S13=13/2(2(7)+(13-1)7)

=13/2(14+84)

=13/2*98

=13*49

=637

Answer 2

The sum of the first 7 multiples of 13 is 364.

Step-by-step explanation:

To find : The sum of the first 7 multiples of 13 ?

Solution :

The 7 multiples of 13 are 13,26,39,...91 are in arithmetic progression.

The sum of n terms of A.P is given by,

$S_n=\frac{n}{2}[a+l]$

where, n=7 is the number of terms,

a=13 is the first term,

l=91 is the last term

Substitute all the values,

$S_7=\frac{7}{2}[13+91]$

$S_7=\frac{7}{2}[104]$

$S_7=7\times 52$

$S_7=364$

Therefore, The sum of the first 7 multiples of 13 is 364.

#Learn more

Q.1- Find the r th term of the A.P. : 1,3,5,7,………..

(a) 2n-1 (b)2r-1 (c) 2r (d) r-2

Q.2- Find the 9th term from the end of the A.P. 7,10, 13,……..,187.

(a) 31 (b)211 (c) 163 (d)141

Q.3 – How many numbers of two digits are divisible by 7? (a) 13 (b)14 (c) 15 (d)16

Q.4- What is the sum of first 100 multiples of 4?

(a) 20100 (b)20200 (c) 20300 (d)20400​

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