The answer for a is 21

Thank u

Thanks Adrian.

sorry, i've lost touch with maths after so long, but can you explain why did you x 6 and why did you x 2? i'm still interested to keep up and refuse to let my brain go rusty :P

C + D = 5u + 9u = 14u. So we get 7u x 2 to get 14u. Agree?

ok, then why x 6?

B + C + D = 10u + 14u = 24u. So we get 4u x 6 to get 24u. Agree?

i see now...thank you:)

Tan Junhong thanks for the reply. My working process using my model is as below: 36 - 20 = 16 Walking time: 16 / (3-1) * 3=24 Equivalent of cycling time: 24/3=8 Thus, cycling of 8 minutes is 2000 meters Hence, total distance: 2000/8*20=5000 But not sure whether a better and easier understandable approach is available?

Your method is the same as mine. Personally, I think it's the easiest way.

The extra 16 min is due to walking a distance of 2000 m, at 1/3 of the cycling speed. Let the cycling time for the 2000 m be t min. Then the corresponding walking time is 3t min. 2t = 16 t = 8 For the cycling journey 8 min --> 2000 m 20 min --> 5000 m The distance is 5000 m

Nowadays China students use the algebraic method to solve this problem in primary school. Let v be the cycling speed. Students use an education 6000/v + (20v-2000)/v = 36 ; or simply, 6000/v - 2000/v = 16 to find v, then Distance = 20v = 5000

Icic: )

Let the cycling speed be v m/min. Then the walking speed is v/3 m/min. For cycling the whole journey, distance travelled = 20v m. For walking 2000 m, time taken = 2000/(v/3) min. For cycling the remaining journey, time taken = (20v - 2000)/v min. Total time taken = 36 min. Thus, 6000v + (20 - 2000/v) = 36 4000/v = 16 v = 4000/16 = 250 Total distance = 20v = 5000 m In this way we do not use the inverse proportion relationship between time and speed.

An alternative method： Consider 2000 = vt = (v/3)(3t), where v and t are in m/min and min respectively. For the same distance travelled, when the speed is v/3, the time taken is 3t. (This is inverse proportion.) The walking time is 2t more than the cycling time. Therefore, 2t = 16 t = 8 From 2000 = 8v, v = 250 Total distance = 20v = 5000 m

This type of problems are more appropriate for algebra at secondary school level, not for Singapore PSLE.

Thanks all for the sharing. Possibly I get to read through all the math text books to get a feel about the progress

Unitary Method

Thanks all. It is correct!