roughworks

UCEED 2018

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UCEED2018Q16·nat·Hard

Shown in the figure is a pyramid with a square base, formed by vertices EFGH and a top vertex I. The diagonally opposite vertices, EG and FH are connected to form the vertex J at their intersection. The vertices I and J are also connected as shown. How many triangles are formed by all these vertices?

Shown in the figure is a pyramid with a square base, formed by vertices EFGH and a top vertex I. The diagonally opposite vertices, EG and FH are connected to form the vertex J at their intersection. The vertices I and J are also connected as shown. How many triangles are formed by all these vertices?