Thanks Adrian. Very clear.

I beg to differ. At 1pm, they are 400km apart. Within the 1 h, from 1pm to 2pm, east bound train traveled another 70km and west bound train traveled another 50 km. The gap is reduced to 400 - 70 - 50 =280 km which should be the answer to (b).

Both train left the same station towards opposite direction, so the distance apart should increase.

If they are moving in the same direction and one train us faster than the other, the distance apart increases. But they are moving in opposite direction towards each other. Shouldn't the distance apart decreases? Unless they had cross each other between 1pm and 2 pm, the they move further apart. Which is not the case.

<------- 1 train westwards (station) 1 train eastwards ------->

Tx :-D

Need more explanation

Both items have 8kg more than its average. The difference between the two average is 2kg. Thus 8kg is the difference of the average.

Thanks Shirley and Vei Li

Here's a video on the solution http://youtu.be/NKVLFj2lwSQ?hd=1

weiqiang...you are good!!

Erm... Annie Lim.. Thanks for your compliment.. I'm still learning everyday... Cheers

Can I check if everyone can view the video properly?

Definitely Tan Weiqiang.. The video is good..very clear explanation... Thank You Sir!!

Welcome! Love the positive feedback!

please do subscribe and share the videos with your friends! :)

Hi Tan Weiqiang,thanks for the effort 😊

Weiqiang my son finds your explanation clear & good. Thanks!

Thank you Janice Chan...You're welcome Tay Ling