Q&A - PSLE Math

[tianzhu]

lynntan15:

someone pls help. thks.

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Q1) Sally, Yiling and Ali shared a bag of beads. Sally received 3/4 of the bag of beads and 3/4 of a bead. Yiling received 3/4 of the remaining bag of beads and 3/4 of a bead. Ali received th last bead in the bag. ___ missing information ___

Hi

I think some information is missing from your question.

What does the question setter want the students to do?

Find the total number of beads? How many beads did Sally receive? or ......

Please refer to this similar type of question which was posted in one of the earlier posts.

Best wishes

http://farm5.staticflickr.com/4019/4713599224_8f586290c0_z.jpg\">

[tianzhu]

Hi PSLE 2012 students


This question from 2DMommy is quite an interesting one.

Best wishes

5 workers take 3 hour 40 mins to paint a house if every worker paints at the same rate and all start and end at the same time. If one of them leaves after painting for an hour, how long will it take the remaining workers to complete the job after the worker has left ?

[lynntan15]

Sorry,, here the correct Qns: -


Sally, Yiling and Ali shared a bag of beads. Sally received 3/4 of the bag of beads and 3/4 of a bead. Yiling received 3/4 of the remaining bag of beads and 3/4 of a bead. Ali received th last bead in the bag. How many beads did Sally received?
(no bead was to be divided in any way.)

[tianzhu]

lynntan15:

Sorry,, here the correct Qns: -


Sally, Yiling and Ali shared a bag of beads. Sally received 3/4 of the bag of beads and 3/4 of a bead. Yiling received 3/4 of the remaining bag of beads and 3/4 of a bead. Ali received th last bead in the bag. How many beads did Sally received?
(no bead was to be divided in any way.)

Hi

Please study the solution for the similar question.

The answer to your question is 24

1unit ----- 1+3/4 -----7/4
4 units ------7

1 part ------- 7 + 3/4
3 parts ------ 23 + 1/4

Sally ------- 23 +1/4 + 3/4 ------- 24

Best wishes

http://farm5.staticflickr.com/4019/4713599224_8f586290c0_z.jpg\">

[jewelbox]

Hi appreciate any help to solve the following qns :

1. Class A and Class B have the same number of pupils. The ratio of the number of boys in Class A to the number of boys in Class B is 3:2. The ratio of the number of girls in Class A to the number of girls in Class B is 3:5. Find the ratio of the number of boys in Class A to the number of girls in Class B. Ans: 6:5

2. I have some red and blue ribbons in a bottle. if I add in 20 red ribbons, 60% of my ribbons are blue. If i add in another 60 blue ribbons, 75% of my ribbons are blue. How many ribbons have I in the bottle. Ans: 180 ribbons

3. In a club, the ratio of women to men was 2:3. 3 more women and 2 more men joined the club. The ratio of women to men then became 3:4. How many men were there in the club at first? Ans: 18 men

Many thanks:)

[tianzhu]

jewelbox:

3. In a club, the ratio of women to men was 2:3. 3 more women and 2 more men joined the club. The ratio of women to men then became 3:4. How many men were there in the club at first? Ans: 18 men

Hi

You may use \"Units and Parts\"

At first
women: men ------- 2u:3u

Change
women: men ------- 3:2

In the end
women: men ------- 3p:4p

Equalise the parts.

(2u + 3) ----- 3p
(x4)
8u + 12 ------ 12p

(3u + 2) ----- 4p
(x3)
9u + 6 ------12p

8u + 12 ----- 9u + 6
1u ------ 6

Number of men in the club at first ------ 3*6 ------ 18

Best wishes

[tianzhu]

jewelbox:

1. Class A and Class B have the same number of pupils. The ratio of the number of boys in Class A to the number of boys in Class B is 3:2. The ratio of the number of girls in Class A to the number of girls in Class B is 3:5. Find the ratio of the number of boys in Class A to the number of girls in Class B. Ans: 6:5

Hi

In this question, a student needs to see that the ratios representing the boys and girls are of different measures and kinds. One needs to differentiate the ratios showing boys and girls.

Let’s have units for boys and parts for girls.MD would come in handy for this question. Due to time constraints, I am not drawing it, but shall give you some pointers.

Boys ----- A : B ------ 3u : 2u
Girls ----- A : B ------ 3p : 5p

Class A and Class B have the same number of pupils.

3u + 3p ----- 2u + 5p
Hence, 1u ----- 2p

Boys ----- A : B ------ 6p : 4p
Girls ----- A : B ------ 3p : 5p

The ratio of the number of boys in Class A to the number of girls in Class B ----- 6:5

Best wishes

[tianzhu]

jewelbox:

2.I have some red and blue ribbons in a bottle. if I add in 20 red ribbons, 60% of my ribbons are blue. If i add in another 60 blue ribbons, 75% of my ribbons are blue. How many ribbons have I in the bottle. Ans: 180 ribbons

Hi

This question was discussed in our earlier posts. Depending on one’s interpretation of the word another in the second condition, one may end up with 180 or 80.

Please confirm with your teacher.

Condition1
Red : Blue -------- change add 20 red ribbons
2u:3u

Condition 2
Red : Blue -------- change add 60 blue ribbons
1p:3p

2u – 20 ------ 1p
3u+60 -------3p

Equalising the parts

6u – 60 -------3p

3u+60 ------- 6u-60
3u ------ 120
1u ------ 40

Number of ribbons at first ------ (5*40)-20 ------180

Please refer to an example for a similar question.

Best wishes

http://farm8.staticflickr.com/7146/6728816353_e2a7aca824_z.jpg\">

[Winx5015]

Hi,


Got problem with the following question. Pse help.

A coin box contained some 10-cent coins and 50-cent coins in the ratio of 7:2. Peter took out eight 10-cent coins and put in another twenty 50-cent coins into the box. There are now half as many 10-cent coins as 50-cent coins.
(a) How many 10-cent coins were in the box at first?
(b) What is the total value of all the coins in the box now?

Thanks!

[tianzhu]

Winx5015:

Hi,


Got problem with the following question. Pse help.

A coin box contained some 10-cent coins and 50-cent coins in the ratio of 7:2. Peter took out eight 10-cent coins and put in another twenty 50-cent coins into the box. There are now half as many 10-cent coins as 50-cent coins.
(a) How many 10-cent coins were in the box at first?
(b) What is the total value of all the coins in the box now?

Thanks!

Hi

You may use \"Units and Parts\"

At first
10-cent coins: 50-cent coins ------- 7u:2u

Change
10-cent coins: 50-cent coins ------- -8 :+20

In the end
10-cent coins: 50-cent coins ------- 1p:2p


Equalise the parts.

(7u - ----- 1p
(x2)
14u - 16 ------ 2p

(2u + 20) ----- 2p

14u - 16 ----- 2u + 20
12u ----- 36
1u ------ 3

Number of 10-cent coins were in the box at first ------ 3*7 ------ 21

Now
Number of 10-cent coins ------ 13
Number of 50-cent coins ------- 26

Total value ------- $14.30

Best wishes