The length of DE in centimetres is 12 .
The following proportion can be established as follow:
AB / DE = BC / EF = AC / DF
Therefore,
let's find DE as follows;
AB / DE = BC / EF
4 / DE = 3 / 9
cross multiply
9 × 4 = 3DE
divide both sides by 3
DE = 36 / 3
DE = 12 cm
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