Respuesta :
An arithmetic progression is simply a progression with a common difference among consecutive terms.
- The sum of multiplies of 6 between 8 and 70 is 390
- The sum of multiplies of 5 between 12 and 92 is 840
- The sum of multiplies of 3 between 1 and 50 is 408
- The sum of multiplies of 11 between 10 and 122 is 726
- The sum of multiplies of 9 between 25 and 100 is 567
- The sum of the first 20 terms is 630
- The sum of the first 15 terms is 480
- The sum of the first 32 terms is 3136
- The sum of the first 27 terms is -486
- The sum of the first 51 terms is 2193
(a) Sum of multiples of 6, between 8 and 70
There are 10 multiples of 6 between 8 and 70, and the first of them is 12.
This means that:
[tex]\mathbf{a = 12}[/tex]
[tex]\mathbf{n = 10}[/tex]
[tex]\mathbf{d = 6}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{10} = \frac{10}2(2*12 + (10 - 1)6)}[/tex]
[tex]\mathbf{S_{10} = 390}[/tex]
(b) Multiples of 5 between 12 and 92
There are 16 multiples of 5 between 12 and 92, and the first of them is 15.
This means that:
[tex]\mathbf{a = 15}[/tex]
[tex]\mathbf{n = 16}[/tex]
[tex]\mathbf{d = 5}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{16} = \frac{16}2(2*15 + (16 - 1)5)}[/tex]
[tex]\mathbf{S_{16} = 840}[/tex]
(c) Multiples of 3 between 1 and 50
There are 16 multiples of 3 between 1 and 50, and the first of them is 3.
This means that:
[tex]\mathbf{a = 3}[/tex]
[tex]\mathbf{n = 16}[/tex]
[tex]\mathbf{d = 3}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{16} = \frac{16}2(2*3 + (16 - 1)3)}[/tex]
[tex]\mathbf{S_{16} = 408}[/tex]
(d) Multiples of 11 between 10 and 122
There are 11 multiples of 11 between 10 and 122, and the first of them is 11.
This means that:
[tex]\mathbf{a = 11}[/tex]
[tex]\mathbf{n = 11}[/tex]
[tex]\mathbf{d = 11}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{16} = \frac{11}2(2*11 + (11 - 1)11)}[/tex]
[tex]\mathbf{S_{11} = 726}[/tex]
(e) Multiples of 9 between 25 and 100
There are 9 multiples of 9 between 25 and 100, and the first of them is 27.
This means that:
[tex]\mathbf{a = 27}[/tex]
[tex]\mathbf{n = 9}[/tex]
[tex]\mathbf{d = 9}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{9} = \frac{9}2(2*27 + (9 - 1)9)}[/tex]
[tex]\mathbf{S_{9} = 567}[/tex]
(f) Sum of first 20 terms
The given parameters are:
[tex]\mathbf{a = 3}[/tex]
[tex]\mathbf{d = 3}[/tex]
[tex]\mathbf{n = 20}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{20} = \frac{20}2(2*3 + (20 - 1)3)}[/tex]
[tex]\mathbf{S_{20} = 630}[/tex]
(f) Sum of first 15 terms
The given parameters are:
[tex]\mathbf{a = 4}[/tex]
[tex]\mathbf{d = 4}[/tex]
[tex]\mathbf{n = 15}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{15} = \frac{15}2(2*4 + (15 - 1)4)}[/tex]
[tex]\mathbf{S_{15} = 480}[/tex]
(g) Sum of first 32 terms
The given parameters are:
[tex]\mathbf{a = 5}[/tex]
[tex]\mathbf{d = 6}[/tex]
[tex]\mathbf{n = 32}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{32} = \frac{32}2(2*5 + (32 - 1)6)}[/tex]
[tex]\mathbf{S_{32} = 3136}[/tex]
(g) Sum of first 27 terms
The given parameters are:
[tex]\mathbf{a = 8}[/tex]
[tex]\mathbf{d = -2}[/tex]
[tex]\mathbf{n = 27}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{27} = \frac{27}2(2*8 + (27 - 1)*-2)}[/tex]
[tex]\mathbf{S_{27} = -486}[/tex]
(h) Sum of first 51 terms
The given parameters are:
[tex]\mathbf{a = -7}[/tex]
[tex]\mathbf{d = 2}[/tex]
[tex]\mathbf{n = 51}[/tex]
The sum of n terms of an AP is:
[tex]\mathbf{S_n = \frac n2(2a + (n - 1)d)}[/tex]
Substitute known values
[tex]\mathbf{S_{51} = \frac{51}2(2*-7 + (51 - 1)*2)}[/tex]
[tex]\mathbf{S_{51} = 2193}[/tex]
Read more about arithmetic progressions at:
https://brainly.com/question/13989292
