A P6 Math Question

Ahm97sic SG

A PSLE Prelim question from one of the top 10 primary schools.

The triangle ABC is an isosceles triangle.
Find the area of the triangle ABC.

A
l \
l***\
l*****\
l******\ 12 cm
l********\
l_********\
l_l______\ C
B

skythewood SG

since isoc, the other 2 angle is 45 degree.

hence, find the height

area of triangle is h x b x half.

newcomer SG

claps claps claps

Ahm97sic SG

Hi Skythewood,

Your answer is not correct. The question requires the answer to be an actual number in cm^2. Please take note that the given length of AC is 12 cm. The solving of this question does not require the use of Pythagoras Theorem as it is a PSLE maths question.

Thank you for your kind attention.

Regards,

ahm97sic

maurizio13 SG

Simple.

Anyway your diagram don't look like isosceles triangle.

Draw 4 triangles = 1 square

Area of square = 12 x 12 = 144

Area of 1 triangle = 1/4 x 144 = 36

Hope that answers your question.

weewee SG

Simple.

Anyway your diagram don't look like isosceles triangle.

Draw 4 triangles = 1 square

Area of square = 12 x 12 = 144

Area of 1 triangle = 1/4 x 144 = 36

Hope that answers your question.

Since the angles are 45, 45, 90, that's why you can draw 3 more triangles to form a 12 by 12 square. From there, divide by four.

skythewood SG

Hi Skythewood,

Thank you for your kind attention.

Regards,

ahm97sic

ooo.. cannot use pythygoras theorem ah.

Ahm97sic SG

Hi Skythewood,

Maurizio13 did not use the Pythagoras Theorem to solve the question. He drew a square of side 12 cm on the side AC. When the area of this square is divided into 4 equal triangles, the area of each triangle is 144/4 = 36 cm^2. The area of one triangle is the same as the area of the triangle ABC, so the area of the triangle ABC is 36 cm^2.

Thank you for your kind attention.

Regards,

ahm97sic

PS : Maurizio13, sorry for the drawing of the triangle. It is not possible to draw or type mathematical signs in the forum.

skythewood SG

Hi Skythewood,

Thank you for your kind attention.

Regards,

ahm97sic

PS : Maurizio13, sorry for the drawing of the triangle. It is not possible to draw or type mathematical signs in the forum.

i think my previous post went gibblish, but nvm...

your primary 6 kid will probably use AC=12 cm as base, and draw a line down to find the height. cos they are kids, only know h x b x half.

after drawing the line down, they will realised they have cut the triangle to 2 halves, look at the left half, it is a isoc. triangle! so by isoc. triangle rule, the height is 6 cm.

than apply back the h x b x half.

so solve question by drawing one line, not by drawing 3 more triangle.

sorry about the gliblish that was posted.