Thank. May i ask, why 2 is used ?

2 taps of each type are used.

Just saying......this is a multiple choice question, so naturally one would like to be able to solve this without much fanfare. The approach that I will propose below is not for every student but I believe there is nothing wrong in sharing an alternative. I guesstimate a lot. In other words I may choose not to use every piece of information available to arrive at a choice, hence guesstimate is predominantly used in multiple choice questions. In the question there are four choices. Choices (1) and (2) are not possible. Tap B is the slowest flowing tap. If both Tap A and Tap C can fill an empty tank in 3 hours, 2 Tap A's and 2 Tap C's (four such taps have a higher combined flow than Tap A, Tap B and Tap C combined) can at best fill an empty tank in an hour and a half. An hour and a half is a longer duration than (1) 3/4 h and (2) 3/8 h. Hence (1) and (2) can be ruled out. Option (4) is also impossible. If the slowest tap (Tap B) and the slower tap (Tap C) can both fill an empty tank in 6 hours, the combined flow of three taps A, B and C cannot be taking more time to fill the same empty tank. That leaves only option (3) through elimination. If one is not feeling secure about it, one can of course verify with calculation. This approach, as mentioned, is not for everyone. Our students are trained to crunch out the numbers before they can accept them as the answers. Provided the multiple choice question has no inherent flaw, I am inclined to think that it is worth while to be able to guesstimate when the opportunity arises. Just my two cents, thank you.

Nicole Wong

The approach is correct. To check whether an answer is correct, we can put the answer back in the question and see if it satisfies the conditions: 60% of 330 = 198 330 - 198 = 132. So the answer is also correct.

It's correct. I think the straightforward approach will be: 40% -> $132 10% -> $132 /4 = $33 100% -> $33 x 10 = $330

Thanks 😊

Convert % to Fraction 60% = 3/5 Spend = 3 units, Total = 5 units, Left = 2 units 2 units = 132 5 units = (132/2) x 5 = 330

Systematic approach is to convert whole number, decimal, ratio, % into fraction, reduce to lowest term and allocate the units

Thank you all! :)

The approach is correct. An alternative way to draw the model is to add 102 to the left side since the same amount is added to both Lin Lin and Mervin. It makes the comparison easier to see that 3 units = 102.

Nice. Thanks so much! This is indeed easier to understand. :)

Tweak the question to see the child is able to apply the same approach: Alice had 5 times as much money as Benny. Both of them donated $30 to the charity. Alice had twice as much money as Benny. How much money did Alice had at first?

Pls explain why 3u =102. Tks

Cheng Liew..maybe u can understand this

Cheng Liew

Because in the end, Lin Lin had twice as much as Mervin, therefore when we look at the two bars, we see that the 102 and 1 unit (which they both have) makes '1 time'. The rest of the 4 units of Mervin's bar will make another '1 time'. By comparing what makes up '1 time', we can conclude that 3 units takes the value of 102. Another way to compare visually is to place the 4 units on top of the 102 + 1 unit and it may be clearer why 3 units = 102.

Thanks all for the detailed explanation. 👍🏼👍🏼👍🏼👍🏼

I got the answer as 134 pies

Working Backwards

Left 12 before gave to Adam 2 Total-> 14(half) 28 before selling to Adam. 28+3(give to Jane) 31(half)-> 62 before selling to Jane 62+5(give to Wee) 67(half)- 67x2= 134 pies baked at First

The total number of pies cannot be 45 since Mrs Wee bought half of the number at first -- 45 is not divisible by 2.

Yes, i got 134 pies by working backwards. Izam Marwasi's way is right.

Check back the answer of 134 by following the question.

So grateful for all yours help. Thanks.. 😅

Work backwards after we draw the model...

Main idea here is understanding that volume of water = base area of tank x height of water (since the water takes the shape of the tank). Volume of water added = 6000 cm^3 = 60 x 50 x height added. Therefore height increased = 6000/(60 x 50) = 2 cm. New water level = 3/5 x 30 + 2 = 20 cm.

Thanks for your explanation.