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Question

Assistance Needed with P5 Mathematics Question

Dear all,

I hope this email finds you well. I am a parent of a P5 student. I am reaching out to you for assistance with a P5 mathematics question that my child is struggling with. Thanks a lot!

Best rgds
Gennee

Answer

Hi Gennee,



You can ask your child to imagine it as the wooden blocks he/she
played with when growing up. The bottom triangles, because they
are 5cm apart like the 2 blue triangles at the top-left, can be
shifted left by 7cm to align with the top. So the 7cm gap is moved
to the right as shown above.

Then it is easy to deduce that AB = 7 + 6 - 3 = 10cm since the
triangles are all identical.
(For working, just sketch out the bottom diagram showing the shifted
triangles and add a comment "shift triangles left by 7cm".)

As for area, it is thus: 10 x 6 / 2 = 30 cm2.

Please accept answer if it is useful. Thanks!

 

 

1 Reply 2 Likes ✔Accepted Answer

Yuh hor… I never thought of shifting the triangles 🙂

Excellent answer!

0 Replies 0 Likes

a. Let x be the length of the rectangle (ie. AB)

So if you look at the top 3 triangles, total length occupied by all 3 triangles is x + 5 + x + 3 + x
= 8 + 3x

If you look at the bottom 2 triangles, total length is 7 + x + 5 + x + 6
= 18 + 2x

The 2 total lengths are equal, so
8 + 3x = 18 + 2x
x = 18 – 8 = 10 cm #

b. Area of ABC = 1/2 * base * height
= 1/2 (10) (6)
= 30 cm² #

 

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