Q&A - PSLE Math

[jeysri72]

Can anyone give an explanation and solution for henry park 2011 prelim maths.

Q17:there were 1000 students at the parade ground and indoor sports hall. 40% of the 600 students at the parade ground were girls. 60% of the students at the indoor sports hall were girls. After some of the students in both venues moved from one venue to the other, 30% of the students in the parade ground and 70% of the students at the indoor sports hall were girls. How many students were there in the indoor sports hall after the movement had taken place? Ans: 450
Q18: A large warehouse had a total of 2180 black, red and white t-shirts for sale. the ratio of black t shirt to red t shirts was 3:1. after 2/5 of the black t shirts and 1/3 of the white t shirts and none of the red t shirts were sold, there were 1504 t shirts left. how many red t shirts were there at first? ans: 380

[mumwgals]

Thank you so much, tainzhu! Your explaination is brilliant!! :thankyou:

[pensiveowl]

hi

Blue beads as % of initial total = 40%
Red beads left as % of initial total = 60% x 60% = 36%
% left = 76% of initial total = 760, so 1% = 10
Red beads lost = 40% x 60 % = 24% = 24 x 10 = 240 beads.

cheers.[/quote]


Thanks also MathIzzzFun

[raghupavithra]

Jia Hui had 350 jelly beans. 52% of them were orange flavoured. She ate some of the orange flavoured jelly beans and the percentage of orange flavoured jelly beans decreased to 44%. How many orange flavoured jelly beans did Jia Hui eat?

[raghupavithra]

Terry bought a vase which he decides to sell. If he sells the vase at a discount of 20%, he makes a gain of $150. If he sells it at a 45%, he loses $325. How much did Terry pay for his vase?

[atutor2001]

raghupavithra:

Terry bought a vase which he decides to sell. If he sells the vase at a discount of 20%, he makes a gain of $150. If he sells it at a 45%, he loses $325. How much did Terry pay for his vase?

Must know :
Cost Price = Selling Price - Profit
Cost Price = Selling Price + Loss

At 20% discount - let the selling price be 80U
At 45% discount - let the selling price be 55U

Cost Price = 80U - 150
Cost Price = 55U + 325

80U-55U = 25U
325 + 150 = 475

25U = 475
1U = 19

Cost Price = 80U - 150 = 80x19 - 150 = 1370

[raghupavithra]

ID 26587

DifficultyDifficulty
If 2/7​ of a number equals to 4/5​ of another number, what is the smallest difference between the two numbers?

5
9
14
18
how to do this sum pls help?

[corneyAmber]

raghupavithra:

Jia Hui had 350 jelly beans. 52% of them were orange flavoured. She ate some of the orange flavoured jelly beans and the percentage of orange flavoured jelly beans decreased to 44%. How many orange flavoured jelly beans did Jia Hui eat?

No. of orange flavoured jelly beans = 0.52*350 = 182

Let u be the # of orange flavoured jelly beans ate.

(182-u)/(350-u) x 100 = 44
100(182-u) = 44(350-u)
18200 - 100u = 15400 - 44u
56u = 2800
u = 50

Hence number of orange flavoured jelly beans ate is 50.

[MathIzzzFun]

raghupavithra:

Jia Hui had 350 jelly beans. 52% of them were orange flavoured. She ate some of the orange flavoured jelly beans and the percentage of orange flavoured jelly beans decreased to 44%. How many orange flavoured jelly beans did Jia Hui eat?

Hi

another approach.. Number of other flavoured jelly beans remained unchanged.

Initially, other flavoured jelly beans = 48% = 168
In the end, other flavoured jelly beans = 100% - 44% = 56% = 168
Total number of jelly beans, in the end = 168 / 0.56 = 300

Number of orange flavoured jelly beans Jia Hui ate = 350 - 300 = 50

cheers.

[pecalis]

ksi:

raghupavithra:

Jia Hui had 350 jelly beans. 52% of them were orange flavoured. She ate some of the orange flavoured jelly beans and the percentage of orange flavoured jelly beans decreased to 44%. How many orange flavoured jelly beans did Jia Hui eat?

No. of orange flavoured jelly beans = 0.52*350 = 182

Let u be the # of orange flavoured jelly beans ate.

(182-u)/(350-u) x 100 = 44
100(182-u) = 44(350-u)
18200 - 100u = 15400 - 44u
56u = 2800
u = 50

Hence number of orange flavoured jelly beans ate is 50.

Alternate Solution using %:
No. of non-orange flavoured remains the same i.e. 350-182=168
This no. is changed to 100-44=56%
56%--->168
44%--->168*44/56 = 132
No. of orange flavoured eaten = 182-132 = 50