Q&A - PSLE Math

[pixiedust]

Suz855:

Need help,


The difference between thrice my age 3 years later and thrice my age 3 years ago equals my present age. What is my present age?

Is the answer 6 or 18 or both acceptable. Thanks :oops:

I plucked in the answers to check. Answer is 18.

present age = 18
3 years later, age=18+3=21, thrice age=63
3 years ago, age=18-3=15,thrice age=45
difference=63-45=18 <right>

present age = 6
3 years later, age=6+3=9, thrice age=27
3 years ago, age=6-3=3,thrice age=9
difference=27-9=18 <wrong>

[pixiedust]

beanbear:

I need help with this sum. The answer given was 56.


The total number of boys was 100% more than the total number of girls in Class A and Class B. The ratio of the number of boys to the number of girls in Class A was 4:3 and the ratio of the number of boys to the number of girls in Class B was 6:1. If there were 8 more boys in Class A than in Class B, find the number of pupils in Class A.

Class A, B:G -> 4u:3u
Class B, B:G -> 6p:1p

Total G=3u+1p
Total B=4u+6p

Since \"The total number of boys was 100% more than the total number of girls in Class A and Class B\", Total B = 2*Total G.
Total G*2=6u+2p

Hence,
4u+6p=6u+2p
u=2p

Since \"If there were 8 more boys in Class A than in Class B\",
4u-8=6p
8p-8=6p
p=4
hence u=8

-------------------------------------
check :
p=4,u=8
Class A,Boys=4u=32,Girls=3u=24, total=56.
Class B,Boys=6p=24,Girls=1p=4,total=28
All clues matched.

[Essential]

Good morning Tianzhu, thank you for your quick reply. Thank you very much

[beanbear]

pixiedust:

beanbear:

I need help with this sum. The answer given was 56.


The total number of boys was 100% more than the total number of girls in Class A and Class B. The ratio of the number of boys to the number of girls in Class A was 4:3 and the ratio of the number of boys to the number of girls in Class B was 6:1. If there were 8 more boys in Class A than in Class B, find the number of pupils in Class A.

Class A, B:G -> 4u:3u
Class B, B:G -> 6p:1p

Total G=3u+1p
Total B=4u+6p

Since \"The total number of boys was 100% more than the total number of girls in Class A and Class B\", Total B = 2*Total G.
Total G*2=6u+2p

Hence,
4u+6p=6u+2p
u=2p

Since \"If there were 8 more boys in Class A than in Class B\",
4u-8=6p
8p-8=6p
p=4
hence u=8

-------------------------------------
check :
p=4,u=8
Class A,Boys=4u=32,Girls=3u=24, total=56.
Class B,Boys=6p=24,Girls=1p=4,total=28
All clues matched.

Thanks much pixiedust! Nice to see you here. I'm :imdrowning: with doing all these maths sums with DS!!

[beanbear]

I need help with this one. Ans given for (a) 3:20 and (b) 56.


An equal number of men and women were at a party. The ratio of the number of women who wore watches to the number of men who wore watches was 3:11. The ratio of the number of women to the number of men who did not wear watches was 5:3.
(a) Find the ratio of the number of women who wore watches to the number of women who did not wear watches.
(b) When 7 times as many men as women left the party, the ratio of the number of men to the number of women who remained at the party became 35:38. If 560 men remained at the party, how many men left the party?

[MathIzzzFun]

Suz855:

Need help,


The difference between thrice my age 3 years later and thrice my age 3 years ago equals my present age. What is my present age?

Is the answer 6 or 18 or both acceptable. Thanks :oops:

Hi

hope this MD helps ..


http://i49.tinypic.com/c877q.jpg\">

cheers.

[MathIzzzFun]

beanbear:

I need help with this one. Ans given for (a) 3:20 and (b) 56.


An equal number of men and women were at a party. The ratio of the number of women who wore watches to the number of men who wore watches was 3:11. The ratio of the number of women to the number of men who did not wear watches was 5:3.
(a) Find the ratio of the number of women who wore watches to the number of women who did not wear watches.
(b) When 7 times as many men as women left the party, the ratio of the number of men to the number of women who remained at the party became 35:38. If 560 men remained at the party, how many men left the party?

Hi

this was discussed earlier -
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&hilit=An+equal+number+of+men&start=6990

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&hilit=An+equal+number+of+men&start=7010

cheers.

[Michaelia0816]

Can I have the statement for the following question, I do not wish to do Guess and Check so pls use another way,


Maria and Santos each had the same amount of money. Each day,Maria spent $12 and Santos spent $6 more than Maria. When Santos had spent all of his money, Maria had $72 left. How much money did Santos have at first?

[tianzhu]

Michaelia0816:

Can I have the statement for the following question, I do not wish to do Guess and Check so pls use another way,


Maria and Santos each had the same amount of money. Each day,Maria spent $12 and Santos spent $6 more than Maria. When Santos had spent all of his money, Maria had $72 left. How much money did Santos have at first?

Hi girl

One possible way is to find the number of days they took to save the money first.

Maria had $72 left because she spent $6 less than Santos.

Number of days she needed to save $72 ------ 72/6 ------ 12

Santos had (18*12) or 216.

Another way, use UM or MD.

Maria: Santos ------ 12:18 ------- 2:3

Maris ------ 2 units + 72

Santos ------- 3 units

1 unit ------- 72

3 units ------- 216

Best wishes

[Michaelia0816]

Thank, I do not like to use guess and check