Respuesta :
Answer:
The total number of marbles in the set is 107 marbles
Step-by-step explanation:
The parameters given are;
Let the size of the marbles be 1 unit
The marbles are arranged to form the equilateral triangle as follows;
1st row = 1 marble
2nd row = 2 marbles and so on so that the total number of marbles for an arithmetic series as follows;
Total number of marbles, t = 1 + 2 + 3 + ... + n
Therefore;
[tex]t = \dfrac{1 + n}{2} \times n[/tex]
Since there are 2 marbles left in forming the first equilateral triangle, we have the total number of marbles in the set, t₁, is given as follows;
[tex]t_1 = \dfrac{1 + n}{2} \times n + 2[/tex]
When the same marble set are arranged into a triangle in which each side has one more marble than in the first arrangement, there where 13 marble shortage, hence, the total number of marbles is given as follows;
[tex]t_1 = \dfrac{1 + (n+1)}{2} \times (n+1) -13[/tex]
We therefore have;
[tex]t_1 = \dfrac{1 + n}{2} \times n + 2 = \dfrac{1 + (n+1)}{2} \times (n+1) -13[/tex]
Which gives;
[tex]\dfrac{n^{2}+n+4}{2}=\dfrac{n^{2}+3\cdot n-24}{2}[/tex]
Therefore;
n² + n + 4 = n² + 3·n - 24
2·n = 24 + 4 = 28
n = 14
From which we have;
[tex]t_1 = \dfrac{1 + 14}{2} \times 14 + 2 = 107[/tex]
Therefore, the total number of marbles in the set, t₁ = 107 marbles.
The number of marbles in the set would be as follows:
[tex]107[/tex] marbles
Arrangement
Given that,
After arranging the marbles in an equilateral Δ, 2 marbles would be left
The size of marble being 1 unit,
So,
The first row of the equilateral Δ will consist of 1 marble,
while
The second row comprises of 2 marbles.
The process goes so on and on.
Therefore,
Total marbles [tex]t = 1 + 2 + 3 + ... + n[/tex]
Hence,
[tex]t = (1 + n)/2[/tex] × n
Because 2 marbles are extra,
[tex]t = (1 + n)/2[/tex] × n [tex]+ 2[/tex]
In case,
The same marble set are framed into a triangle, every side would contain 1 marble exceeding the previous one where 13 marbles would be felt short.
Thus,
Total marbles = [tex]\frac{1 + (n + 1)}{2}[/tex] × [tex](n + 1) - 13[/tex]
by putting the values, we get
[tex]n^2 + n + 4 = n^2 + 3n - 24\\2n = 24 + 4 = 28\\n = 14[/tex]
∵ Total marbles [tex]= (1+ 14)/2[/tex] × [tex]14 + 2[/tex]
[tex]= 107[/tex]
Thus, 107 marbles are the correct answer.
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