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primary 5 | Maths
| Area & Volume
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Other than guess and check method, is there other methods to solve this question? How ? Thanks
81 + 36 = 117
Or
Notice that 117 = 13 x 3 x 3
So we can form 13 small squares , each 3cm.
We can arrange them into two bigger squares, one made of four 3cm squares,
(2 small squares by 2 small squares)
and the other made of nine 3cm squares.
Length of the biggest square = 3cm x 3 = 9cm
Length of the middle square = 3cm x 2
= 6cm
FH = HI
Since HI = HG ,(both are sides of the same square)
Then FH = HG
So FG = 2HG
Since FG = 6cm, (see working above)
HG = 6cm ÷ 2 = 3cm
so the smallest square is 3cm by 3cm
Length of DJ = DC + CG + GJ
= 9cm + 6cm + 3cm = 18cm
Area of triangle of ADJ = ½ x AD x DJ
= ½ x 18cm x 9cm
= 81cm²
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