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MATH / The figure below represents a figure with a total of 120 triangles and n points labeled as vertices on the horizontal base. What is the value of n? [asy]size(250,400); pair P = (3,…

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problem

The figure below represents a figure with a total of 120 triangles and nn points labeled as vertices on the horizontal base. What is the value of nn? [asy]size(250,400); pair P = (3,4); real r = .05; draw((0,0)--P); draw((1,0)--P); draw((3,0)--P); draw((4.5,0)--P); draw((7,0)--P); draw((7,0)--(8,0)); fill(circle((8+3r,0),r)); fill(circle((8+7r,0),r)); draw((8+15r,0)--(9+15r,0)); draw((9+15r,0)--P); draw((11+15r,0)--P); fill(circle((8+11r,0),r)); draw((0,0)--(7,0)); draw((9+15r,0)--(11+15r,0)); label("PP",P,N); label("A1A_1",(0,0),S); label("A2A_2",(1,0),S); label("A3A_3",(3,0),S); label("A4A_4",(4.5,0),S); label("A5A_5",(7,0),S); label("An−1A_{n-1}",(9+15r,0),S); label("AnA_n",(11+15r,0),S);[/asy]
Plain-text mathematical notation (without MathML)
The figure below represents a figure with a total of 120 triangles and n points labeled as vertices on the horizontal base. What is the value of n?

[asy]size(250,400);
pair P = (3,4);
real r = .05;
draw((0,0)--P); draw((1,0)--P); draw((3,0)--P); draw((4.5,0)--P); draw((7,0)--P); draw((7,0)--(8,0)); fill(circle((8+3r,0),r)); fill(circle((8+7r,0),r)); draw((8+15r,0)--(9+15r,0)); draw((9+15r,0)--P); draw((11+15r,0)--P); fill(circle((8+11r,0),r)); draw((0,0)--(7,0)); draw((9+15r,0)--(11+15r,0));
label("P",P,N); label("A₁",(0,0),S); label("A₂",(1,0),S); label("A₃",(3,0),S); label("A₄",(4.5,0),S); label("A₅",(7,0),S); label("A_(n−1)",(9+15r,0),S); label("A_(n)",(11+15r,0),S);[/asy]
Original LaTeX notation
The figure below represents a figure with a total of 120 triangles and $n$ points labeled as vertices on the horizontal base. What is the value of $n$?

[asy]size(250,400);
pair P = (3,4);
real r = .05;
draw((0,0)--P); draw((1,0)--P); draw((3,0)--P); draw((4.5,0)--P); draw((7,0)--P); draw((7,0)--(8,0)); fill(circle((8+3r,0),r)); fill(circle((8+7r,0),r)); draw((8+15r,0)--(9+15r,0)); draw((9+15r,0)--P); draw((11+15r,0)--P); fill(circle((8+11r,0),r)); draw((0,0)--(7,0)); draw((9+15r,0)--(11+15r,0));
label("$P$",P,N); label("$A_1$",(0,0),S); label("$A_2$",(1,0),S); label("$A_3$",(3,0),S); label("$A_4$",(4.5,0),S); label("$A_5$",(7,0),S); label("$A_{n-1}$",(9+15r,0),S); label("$A_n$",(11+15r,0),S);[/asy]

level

Level 4

type

Counting & Probability

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