Q&A - P3 Math

[Herbie]

Mrs Lim bought a few chicken pies and apple pies for $38. Each apple pie cost $0.60 and each chicken pie cost 2/3 more than an apple pie. 3/5 of what she bought was apple pie, how many chicken pie did she buy?


Can someone help to solve this qn? Tx

[CoffeeCat]

Herbie:

Mrs Lim bought a few chicken pies and apple pies for $38. Each apple pie cost $0.60 and each chicken pie cost 2/3 more than an apple pie. 3/5 of what she bought was apple pie, how many chicken pie did she buy?


Can someone help to solve this qn? Tx

First find cost of chicken pie = (3+2)/3 times $0.60 = $1.00
3/5 are apple pie, 2/5 are chicken pie, meaning for every 3 apple pies there are 2 chicken pies, so we group this 5 pies together and their cost will be
($0.60 * 3) + ($1.00 * 2) = $3.80

To find number of such groups, divide $38 by $3.80 = 10.
Therefore there are (10 * 2 = 20) chicken pies

[Herbie]

Thanks CoffeeCat,


I have another maths qn. Can help to solve it? Tx

Mr Tan had 1.5 litres of white paint on Tin A and 1.25litres of blue paint in Tin B. He poured 750ml of blue paint from TIn B into Tin A. He then poured some of the mixture in Tin A back into Tin B. if 7/11 of the final mixture in Tin B was made up of blue paint, what does the volume of mixture in Tin A that Mr Tan had poured into Tin B?

[CoffeeCat]

Herbie:

Thanks CoffeeCat,


I have another maths qn. Can help to solve it? Tx

Mr Tan had 1.5 litres of white paint on Tin A and 1.25litres of blue paint in Tin B. He poured 750ml of blue paint from TIn B into Tin A. He then poured some of the mixture in Tin A back into Tin B. if 7/11 of the final mixture in Tin B was made up of blue paint, what does the volume of mixture in Tin A that Mr Tan had poured into Tin B?

Hmm may i ask where you get these qns from? This kinda question used to be challenging and appear in math competition.
The key to solving is to note the ratio of blue to white paint in A after the first transfer.
750 : 1500 = 1: 2.
if 4/11 of the final mixture is white paint, then 2/11 of the final mixture must be the blue paint from A. therefore 5 /11 of final mixture = 0.5 litres. From this you find 6/11 of final mixtures = 0.6litres

[Herbie]

Hi CoffeeCat,


I can’t see how the ratio of 1: 2 is used to solve the problem. Also how you get the 2/11? Can explain in more detail?

Many thanks!

[CoffeeCat]

Herbie:

Hi CoffeeCat,


I can't see how the ratio of 1: 2 is used to solve the problem. Also how you get the 2/11? Can explain in more detail?

Many thanks!

oh because in such \"transfer here transfer there\" question, after the first transfer, it is always assumed thatt he impure mixture will be evenly mixed, thus the ratio is important. Because later when you transfer the impure mixture back, you are transferring a mixture with that ratio of constituents.
In the new mixture in A, you have 2 litres of whitepaint for every 1 litre of blue paint.

[Herbie]

Hi CoffeeCat,


Sorry, to trouble you but i dun know how you get the 2/11?

Can explain with working??

Tx

[CoffeeCat]

Herbie:

Hi CoffeeCat,


Sorry, to trouble you but i dun know how you get the 2/11?

Can explain with working??

Tx

After the first transfer we have an even mixture of white paint to blue paint in A in the ratio of 2: 1.
So in B, if the quantity of white paint brought over is 4/11 (of the new mixture in B), then during the transfer, (4/11) / 2 = 2/11 of (new mixture in B now must be blue paint brought over from A along with that white paint.

[Herbie]

Oh! OK. Now i understand where the 2/11.

Sorry need to ask again where you get the 5/11 and 6/11?


Sorry very loh soh... :stupid:

[CoffeeCat]

It’s ok. After the first transfer of blue paint from B to A, there is 1.25-0.75=0.5 litres of blue paint still remaining in B. Since we now know that 4/11 & 2/11 are from A, the remaining 5/11 must be the blue paint still remaining whichcorresponds to 0.5 litres. The questions eventually ask for the amt of paint transferred from A to B, which corresponds to t he (4+2)/11 = 6/11 of mixture.

Is this your son’s homework?