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## Question

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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