Akila Parthasarathy, this question was posted on 15 April. You might want to look for that post and the solutions offered.

Thank you

This q will have 3 answers unless the question is changed to 90 from 94. Besides 77, try similar triangles AEG and BKG for answer 75. Another one is extend A and D to form a 5-unit rectangle (KB and CL is 1 unit each and BC is 3 units) and find the whole area and then divide by 2 for a third answer 78 and1/3.

Oh ok thank you

Thk u

Q16,it should be 1h 15 min

How to derive it

Rachael Sally... A useful idea for some of these questions is as follow: For the same distance travelled, Speed of A: Speed of B = Time taken by B: Time taken by A. So, for q16. We see that Cindy's speed to Rella's speed is 2:3. Therefore, the time taken by Cindy: the time taken by Rella = 3:2. Hence, the 1 unit difference is 45 min. Hence, Cindy took 3 x 45 min = 135 min (2 hours 15 min).

Thanks but y Cindy is 3?

Because her speed is slower and so she should take a longer time.

The idea comes from the fact that for the same distance: Average Speed of Cindy x Time taken by Cindy = Average Speed of Rella x Time taken by Rella.

So I shld take the latter ratio (Cindy:Rella @ 3:2)? Rather than 1st ratio (Cindy:Rella @ 2:3)?

Oic ok I see it on yr 2nd explanation 👍

Yes. Think of it this way, for the same distance travelled, Cindy's average speed is slower than Rella, right? So, Cindy should take a longer time to complete the same distance. I think you can see why this idea works from my second explanation.

Thanks all for the explanation 👍

😧u guys are smart

In fact, there are a few related ideas that can be derived from this relationship. e.g., for the same time taken, the the distance travelled by A: distance travelled by B = average speed of A: average speed of B

Rachael Sally... when you go through the idea with your child, it will be simpler for you to use some numbers to help the child see the pattern before generalising to the idea.

For 19, remember that speed is distance/time, and you will get the relationship mentioned. Edit: to be accurate, speed is inversely proportional to time, but I use the word 'opposite' to help your girl understand.

Ok qn 16 my gal undstd now. Tq

You can apply a similar idea for q18. For the same distance travelled, Time taken by Ms Snow: Time taken by Ms White = Average Speed of Ms White: Average Speed of Ms Snow. So, we have Speed of Ms White: Speed of Ms Snow = 2:1. So, 1 unit is 20km/h and so 2 units represent 40 km/h.

I'm trying hard to undstd but when I show her yr working she undstd. So she try solve and recheck vs yrs. Tqvm

For your girl to check against if she needs. :)

Thank you Adrian Ng!