Q&A - PSLE Math

[MathIzzzFun]

lee tong fong:

Thanks for your help to solve my earlier questions. I need to further seek your help to solve following using model:



3) 2/9 of Rani’s balloons were red and the rest were green. She gave away 15 green balloons and bought another 25 red balloons. She then had the same number of red and green balloons. How may green balloons did she have at first?

Thanks in advance.

ratio of red balloons : green balloons
= 2/9 : 7/9
--> 2u : 7u

Bought 25 red balloons & give away 15 green balloons, in the end,
number of red balloons : green balloons
= 2u + 25 : 7u - 15
--> 1 : 1

2u + 25 = 7u - 15
5u --> 40, 1u --> 8

Number of green balloons at first = 8 x 7 =56



cheers.

[MathIzzzFun]

lee tong fong:

Thanks for your help to solve my earlier questions. I have further questions to seek your help.


2)\tRavi had a total of 80 pieces of $10 notes and $50 notes. He used ½ of his $10 notes and withdrew another four pieces of $50 notes from the bank. After which, the number of $50 notes he had was 2/5 the number of $10 notes. Find the total value of the 80 pieces of notes he had at first.


Thanks in advance.

In the end,
number of $50 notes : $10 notes
--> 2u : 5u

At first,
number of $50 notes = 2u - 4 (since 4 pieces of $50 were added)
number of $10 notes = 2 x 5u = 10u

Total number of notes at first --> 2u - 4 + 10u = 12u -4

12u - 4 = 80
1u --> 7

At first,
value of $50 notes --> $50 x (2 x 7 -4) = $500
value of $10 notes --> $10 x 10 x 7 = $700
Total $1200

cheers.

[MathIzzzFun]

lee tong fong:

Thanks for your help to solve my earlier questions. I need to further seek your help to solve following using model:


1) Joseph has some local and foreign stamps in 2 boxes. In Box A, the numbers of local and foreign stamps are in the ratio 3: 4. In Box B, the number of local stamps is twice the number of foreign stamps. Joseph transfers half of the foreign stamps from Box A to Box B. The numbers of stamps in Box A become 105 and the ratio of the number of local stamps to the number of foreign stamps in Box B becomes 6:5.
a) How many foreign stamps have been transferred from Box A to Box B?
b) What is the number of stamps in Box B at first?

Thanks in advance.

For Box B-
at first, local : foreign = 2 : 1 = 6u : 3u --> total 9u
in the end, local : foreign = 6u : 5u

foreign stamps added --> 5u-3u = 2u

since half of foreign stamps in Box A was transferred to Box B,
2u --> half of foreign stamps in Box A
originally, foreign stamps in Box A --> 2u x 2 = 4u

at first, local stamps in Box A : foreign stamps in Box A = 3u : 4u
in the end, local stamps in Box A : foreign stamps in Box A = 3u : 2u --> total 5u

5u --> 105, 1u --> 21

a) foreign stamps transferred from A to B = 2 x 21 = 42
b) total number of stamps in Box B at first = 9 x 21 = 189

cheers.

[MathIzzzFun]

happyheart:

Hi,

Need help to solve these using model please.

Q) If Jeremy gives 15 stickers to Ramesh, he will have four times as many stickers as Ramesh. If Ramesh gives 5 stickers to Jeremy, the ratio of Jeremy's stickers to Ramesh stickers would be 14:1. How many stickers does Jeremy have?

Thank you!

Here's the solution using MD... I have the intermediate steps in arriving at the final model..

http://i50.tinypic.com/vzhusx.png\">

cheers.

[lee tong fong]

Thanks for your great help MathIzzzFun and skyed. I have 2 more questions need you to solve if possible use model… Thanks in advance.


1) Jane and Iris had 255 sweet together. Jane had 15 more sweets than Iris. Jane gave away 25% as many sweet as Iris. She was left with twice as many as sweets as Iris.

(a)How many sweets did Iris give away?
(b)How many sweets did Jane have in the end?

2) Sushila went shopping. She spent $588 on 2 dresses, 3 shirts and 2 pairs of
sunglasses. The total amount spent on the dresses was 0.4 of the total amount
spent on the skirts and sunglasses.The total amount spent o the sunglasses was
1/ 3 of the total amount spent on dresses and shirts.

(a)\tHow much did she spend on the 2 pairs of sunglasses?
(b)What was the cost of the third shirt if the average cost of the two shirts was
$88?

[MathIzzzFun]

lee tong fong:

Thanks for your great help MathIzzzFun and skyed. I have 2 more questions need you to solve if possible use model.. Thanks in advance.


1) Jane and Iris had 255 sweet together. Jane had 15 more sweets than Iris. Jane gave away 25% as many sweet as Iris. She was left with twice as many as sweets as Iris.

(a)How many sweets did Iris give away?
(b)How many sweets did Jane have in the end?

http://i47.tinypic.com/2cyppqu.png\">

cheers.

[MathIzzzFun]

lee tong fong:

Thanks for your great help MathIzzzFun and skyed. I have 2 more questions need you to solve if possible use model.. Thanks in advance.


2) Sushila went shopping. She spent $588 on 2 dresses, 3 shirts and 2 pairs of
sunglasses. The total amount spent on the dresses was 0.4 of the total amount
spent on the skirts= shirts ? and sunglasses.The total amount spent o the sunglasses was
1/ 3 of the total amount spent on dresses and shirts.

(a)\tHow much did she spend on the 2 pairs of sunglasses?
(b)What was the cost of the third shirt if the average cost of the two shirts was
$88?

Money spent-
dresses : shirts + sunglasses = 2 : 5
dresses : total (dresses + shirts + sunglasses) = 2 : 7

sunglasses : dresses + shirts = 1 : 3
sunglasses : total = 1 : 4

Total amount spent is the same in both cases,
dresses : total --> 8u : 28u
sunglasses : total --> 7u : 28u
shirts --> 28u - 8u - 7u = 13u

28u --> $588, 1u --> $21


a) amount spent on sunglasses --> 7 x $21 = $147
b) amount spent on shirts --> 13 x $21 = $273
cost of 3rd shirt = $273 - 2 x $88 = $97

cheers.

[lee tong fong]

Thanks MathIzzzFun for your detail working solution.


There an typo error for Jane’s sweet and it should be 255-15/2 instead of 255+15/2 =135

[MathIzzzFun]

lee tong fong:

Thanks MathIzzzFun for your detail working solution.


There an typo error for Jane’s sweet and it should be 255-15/2 instead of 255+15/2 =135

It's correct... you may want draw the model = Jane's block (longer) and Iris's block... to find Jane's sweets --> fill in the \"gap\" ie add 15 to get 2 x Jane's blocks...
so Jane's sweets --> (255 + 15) /2 = 135
and Iris's sweets --> (255 - 15)/2 = 120

cheers.

[lee tong fong]

Thanks MathIzzzFun for your contribution. I have 3 more questions that need your help in model or using simultaneous equation .


1)Leon bought some terrapins and guppies for a total of $96. He bought 3 times as many guppies than terrapins. He paid $30 more for the terrapins than for the guppies. Each terrapin cost $10.40 more than each guppy.
a)\tHow many terrapins did he buy?
b)\tWhat was the cost of each guppy?


2)Sally, Yiling and Ali shared a bag of beads. Sally received 3/4of the bag of beads and ¾ of the bead. Yiling received ¾ of the remaining bags of beads and ¾ of the bead. Ali received the last bead in the bag.
How many beads did Sally receive?

3) In the sack of 42 shirts and shorts, 40% of the shirts and 50% of the shorts were soiled. If 24 shirts and shorts were clean, how many soiled shirts and were there?

Thanks in advance