Eric Nicholas K's answer to Aniq's Secondary 4 E Maths Singapore question.

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Eric Nicholas K
Eric Nicholas K's answer
3322 answers (Tutor Details)
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You must use the fact that several triangles are similar before assigning units to the lengths. Note that for two similar triangles PQR and STU, if PQ : ST = 3 : 1, then QR : TU = 3 : 1 and PR : SU = 3 : 1.

For ratios of areas, we square the ratios of the lengths.