TIEW KAI JIE NICHOLAS's answer to championnn's Primary 5 Maths Fractions Singapore question.

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TIEW KAI JIE NICHOLAS
Tiew Kai Jie Nicholas's answer
107 answers (Tutor Details)
1st
Length of Rope A is 7/9 of total length.
From this, we can deduce
Total Rope Length - 9 units
Rope A - 7 units
Rope B + Rope C - 2 units.

Rope B is thrice the length of Rope C.
From this we can deduce
Rope B - 3 units
Rope C - 1 unit
Rope B + Rope C - 4 units

Common item here is the units of Rope B + Rope C, hence, make the number of units the same. Therefore,
Total Length of Rope - 18 units
Rope A - 14 units
Rope B + Rope C - 4 units

Rope A is longer than Rope C by 390cm
14 units - 1 unit = 13 units
13 units = 390cm
1 unit = 30 cm

Total Length of Rope is 18 units
18 units = 540cm