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UKMT Grey Kangaroo, 2021

Combinatorics Difficulty 3.0 AMC 10/12 Find the answer United Kingdom

A triangular pyramid is built with 20 cannonballs, as shown. Each cannonball is labelled with one of A, B, C, D or E. There are four cannonballs with each type of label. The diagrams show the labels on the cannonballs on three of the faces of the pyramid. What is the label on the hidden cannonball in the middle of the fourth face?

(A) $A$ (B) $B$ (C) $C$ (D) $D$ (E) $E$

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