For an estimate, we can choose 170 to multiply with 5cm to yield 850 cm = 8.5 m.

I don't think the choices provided in the question are correct.

The trick is the first sentence. Three triangles....

Hey there Jason. Good evening to you. Actually Vei Li Soo was right about the ratio. Besides 36÷3 = 12 as Vie Li Soo had shown.

Jason Khng, from your diagram, triangle B wouldn't be 1/3 of triangle C

Thanks for the all the responses. The answer is 2 (2/3). I will check with the school teacher the explanation as this is my son P4 online hw. Will update you all again if any updates. Thanks again.

Jane Lee, here's another reasoning for 2/3 to be incorrect: If triangle B is 1/3 of C, then the unshaded part of triangle C would be 2/3 of C. Including triangle A, fraction of unshaded part would have to be more than 2/3.

If the answer is 2/3, the only reason is that there is a typo in "B is 3/9 of C. " It should be "B is 4/9 of C . "

The teacher responded and indeed there's a typo error to the question. Xavier Sng is correct, B is 4/9 of C. With that the answer (2) is justified. Thanks Vei Li Soo, Xavier and Jason for responding to my question.

Thank you for the clarification.

Thanks! Izam Marwasi

For students who need a visual model...

Jasmine, how u get 741?

Play cheat !!

How about 19?

Number of numbers fr 21 to 57

The calculation (21+61)/2 also gives the correct answer because the idea of average is 'even-ing' out the numbers. Since there are pairs of numbers with the same total, taking the first and last number will give the same result. Another point to note is that 41 is sitting in the middle position, which is also the average because this series of numbers is 'symmetrical'.

NOTE: This only works for arithmetic progression.