Q&A - PSLE Math

[cimman]

Beikiasu:

2) A florist had 84 stalks of orchids and 4 times as many stalks of roses in her shop.After buying an equal number of orchids and roses the ratio of the number of orchids to the number of roses became 5:9.How many stalks of orchids and roses did she buy altogether? CHIIJ, 2011, Qusetion 9, 3 mark, Answer 462. Thanks.

here's an alternative approach:
note: black fonts denote values transferred directly from the problem sum, red fonts denotes derived values.
http://i45.tinypic.com/6pcoe1.png\">

here's another approach using only 1 unknown variable:
http://i46.tinypic.com/w81ekp.png\">

here's another variation. Depending on how you want to fill up the blank boxes, there are a few options. However, these are all slight variations on the basic equations. The important thing is to see the links between the boxes. Once you remove the words, you will find that the relationships between the various boxes in the table are quite standard.
http://i47.tinypic.com/30ljkgl.png\">

[Beikiasu]

old school,tianzhu and cimman, :thankyou: :thankyou:

[Beikiasu]

Hi, can someone help me to solve this problem sum?


1) The number of members in a stamp-collectors club increased by 40% from March to April. However, the number of members dropped by 25% from April to May. If the difference in the number of members between March and May was 9, how many members were there in May?ACS, 2011, Questions 10,3 mark, Ans:189

2) The ratio of the number of duck to the number of geese on Farmer Zhou’s farm was 5:6. When Farmer Zhou acquired 242 more ducks, there was an overall increase of 40% of the total number of ducks and geese he had at first.
(a) How many ducks and geese were there on Farmer Zhou’s farm at the end?
(b) What was the percentage increase in the number of ducks on Farmer Zshou’s farm?ACS, 2011,Question 18, 5 mark, Ans:847, 88%

3) The ratio of Jamal’s mass to Katty’s mass is 4:5.Jamal’s mass is increased by 40% and Kathy’s mass is decreased. What percentage of kathy’s mass must be decreased so that thier total mass remains the same?TaoNan, 2011, Question 12, 4 mark, Ans:32%

[Easy-going]

Hi

Can anyone help me with these two problems sums. Thanks

From MY Pals are Here 6A
Pg100
Qn29

[Easy-going]

Hi

Can anyone please help me with these problem sums taken from My Pals are Here Textbook 6A Pg 100
Qn 29
Zac and Sally share some stickers. If Zac gives Sally 1/2 of his stickers, Sally will have 48 more stickers than Zac. If Zac gives 1/4 of his share to Sally, Sally will have 28 more stickers. How many stickers does Zac have at first?

Qn 30
The figure shows the arrangement of lamp posts and trees along a stretch of road. A lamp post is placed after every 4 trees. The distnace between the lamp post and a tree is 1.2m. THere are 45 trees along the road. What is the length of the road?


First tree Second Tree Third Tree Fourth tree Lamppost Fifth tree


I couldn’t upload the diagram. My apology here.
Thanks

[altp10]

Hi. I need help with the following Speed question.


Joel & Cliff ran a 100m race in which Joel crossed the finishing line just as Cliff reached the 90m mark.
a) Since Joel won the first race by 10m, he decided to start the second race 10m behind the starting line. Both boys ran at the same speed as in the first race. Who won the second race?
b) In the third race, Cliff started 10m ahead of the starting line. Again assuming that both boys ran at the same speed as in the first race, who was the winner of this race?

Thank you in advance.

[PapayaDad]

altp10:

Hi. I need help with the following Speed question.


Joel & Cliff ran a 100m race in which Joel crossed the finishing line just as Cliff reached the 90m mark.
a) Since Joel won the first race by 10m, he decided to start the second race 10m behind the starting line. Both boys ran at the same speed as in the first race. Who won the second race?
b) In the third race, Cliff started 10m ahead of the starting line. Again assuming that both boys ran at the same speed as in the first race, who was the winner of this race?

Thank you in advance.

I assume Joel finish the race in 10 seconds. That means his speed is 10 meters per second. At that time (10 second) Cliff only reach 90m ; so Cliff speed is 9 meters per second.

Joel start 10 meters behind, meaning he need to cover 110 meters, his speend is 10 meters per second, so he took 11 seconds.

Cliff speed is 9 meters per second, at 11 second he is at 99meter only, still behind Joel.

Cliff then start 10m in front, need to cover 90 meters, his speed is 9 meter per second, so complete in 10 seconds. Joel also took 10 second to reach. so they reach together.

[tianzhu]

Beikiasu:

3) The ratio of Jamal's mass to Katty's mass is 4:5.Jamal's mass is increased by 40% and Kathy's mass is decreased. What percentage of kathy's mass must be decreased so that thier total mass remains the same?TaoNan, 2011, Question 12, 4 mark, Ans:32%

Hi

Jamal:katty ------ 4:5 ------ 40:50

Jamal's mass is increased by 40% and Kathy's mass is decreased.

Jamal ------ 40*1.4 ------- 56

For their mass to remain the same, katty’a mass must be reduced to 34% (reduced by 16%)

Percentage decrease ------ 16/50*100% ----- 32%

Best wishes

[altp10]

altp10:

Hi. I need help with the following Speed question.


Joel & Cliff ran a 100m race in which Joel crossed the finishing line just as Cliff reached the 90m mark.
a) Since Joel won the first race by 10m, he decided to start the second race 10m behind the starting line. Both boys ran at the same speed as in the first race. Who won the second race?
b) In the third race, Cliff started 10m ahead of the starting line. Again assuming that both boys ran at the same speed as in the first race, who was the winner of this race?

Thank you in advance.

Hi. I think I managed to solve this myself. However would still like to have some advice to confirm my answer.


According to first two sentences, J wins by 10m.
So breaking the 100m into 10 segments of 10m each, J would be faster than C by 1m in every segment. This also mean J runs 11m while C runs 10m.

a) Since J runs 11m (J adds 11) & C runs 10m (C adds 10):
J C
-10 0
1 10
12 20
23 30
34 40
45 50
56 60
67 70
78 80
89 90
100 100
Answer to a) Tie between the 2 boys.

b) Since J runs 11m (J adds 11) & C runs 10m (C adds 10):
J C
0 10
11 20
22 30
33 40
44 50
55 60
66 70
77 80
88 90
99 100
Answer to b) C won.

Please do advise if I'm correct.
Thank you.

(Sorry I can't load any diagrams as I'm typing these using iPhone)

[Oldschool]

[quote="Beikiasu"]Hi, can someone help me to solve this problem sum?


1) The number of members in a stamp-collectors club increased by 40% from March to April. However, the number of members dropped by 25% from April to May. If the difference in the number of members between March and May was 9, how many members were there in May?ACS, 2011, Questions 10,3 mark, Ans:189

March : April : May
= 100% : 140% (increased by 40% of March) : 105% (decrease by 25% of April)

So 5% => 9
100% => 180

In May = 180+9 = 189


2) The ratio of the number of duck to the number of geese on Farmer Zhou’s farm was 5:6. When Farmer Zhou acquired 242 more ducks, there was an overall increase of 40% of the total number of ducks and geese he had at first.
(a) How many ducks and geese were there on Farmer Zhou’s farm at the end?
(b) What was the percentage increase in the number of ducks on Farmer Zshou’s farm?ACS, 2011,Question 18, 5 mark, Ans:847, 88%

So, 40% => 242
100% => 605

Final is 140% = 242 + 605 = 847

At beginning D:G = 5:6
No. of ducks at beginning = (5/11) x 605 = 275

% increase of ducks = (242/275) x 100 = 88%