Q&A - PSLE Math

[iwork]

Q : 2/7 of the notes in a cash box is hundred-dollar notes. The rest of the notes are fifty-dollar and ten-dollar notes. The number of fifty-dollar and ten-dollar notes is 450 more than the number of hundred-dollar notes. The ratio of the number of fifty-dollar notes to the number of ten-dollar notes is 7:8. Find the difference between the total value of the fifty-dollar notes and the total value of the ten-dollar notes in the cash box.

Pls help. Thank you.

Sorry read wrongly. fifty become five.

1. 2/7 is hundred-dollar notes, so 5/7 is others.
2. The difference is 3/7 which is 450, so 1/7 is 150, 5/7 is 850.
3. Now the ratio of 50-dollar to 10-dollar is 7:8, so there are 7/15 x 850=350 50-dollar and 400 10-dollar.
4. total value of 5-dollar notes = 50 x 350 = 17500, total value of 10-dollar notes = 10 x 400 = 4000.
5. Difference in value = 17500 - 4000 = $13500

[Jerico]

Pls help. Tks.

Can someone please help with the following question :-

Q : Andy, Tony and Joseph paid a bill of $126 together after a meal. Andy paid twice as much as Tony and Tony paid thrice as much as Joseph. How much money does Tony and Joseph each have to return to Andy if they were to bear the cost of the meal equally ?

Thanks in adv for your help.

[alfretztay]

Q : 2/7 of the notes in a cash box is hundred-dollar notes. The rest of the notes are fifty-dollar and ten-dollar notes. The number of fifty-dollar and ten-dollar notes is 450 more than the number of hundred-dollar notes. The ratio of the number of fifty-dollar notes to the number of ten-dollar notes is 7:8. Find the difference between the total value of the fifty-dollar notes and the total value of the ten-dollar notes in the cash box.

Pls help. Thank you.

1. 2/7 is hundred-dollar notes, so 5/7 is others.
2. The difference is 3/7 which is 450, so 1/7 is 150, 5/7 is 850.
3. Now the ratio of 5-dollar to 10-dollar is 7:8, so there are 7/15 x 850=350 5-dollar and 400 10-dollar.
4. total value of 5-dollar notes = 5 x 350 = 1750, total value of 10-dollar notes = 10 x 400 = 4000.
5. Difference in value = 4000 - 1750 = $2250

I would solve the question as follows :
5u - 2u = 3u -> 450
1u -> 150
5u -> 750
750/15 =50
50 x 7 = 350
350 x 50 = 17500
50 x 8 = 400
400 x 10 = 4000
17500 - 4000 = 13500
Ans : $13 500.

[alfretztay]

Pls help. Tks.

Can someone please help with the following question :-

Q : Andy, Tony and Joseph paid a bill of $126 together after a meal. Andy paid twice as much as Tony and Tony paid thrice as much as Joseph. How much money does Tony and Joseph each have to return to Andy if they were to bear the cost of the meal equally ?

Thanks in adv for your help.

126/3 = 42

A(6u) + T(3u) + J(1u) -> 126

J : 1u -> 126/10 = 12.6

42 – 12.60 = 29.40

T : 3u -> 37.80

42 – 37.80 = 4.20

Ans : Tony : $4.20 and Joseph : $29.40.

[alfretztay]

Pls need help:

Can somebody pls help me to solve this problem
Anna baked some chicken and beef pies for her friends.45% of the chicken pies and 10% of the beef pies were eaten.Altogether 1/3 of the pies were eaten.In the end,she was left with 10 more chicken pies than beef pies.How many chicken pies did she bake? (Ans 100)
Thanks

C(left) : C(eaten) : C(total)
11 : 9 : 20
B(left) : B(eaten) : B(total)
9 : 1 : 10
Eaten : Total
10 : 30
1 : 3
11u – 9u = 2u
2u -> 10
1u -> 5
20u -> 100
Ans : 100 chicken pies.

[alfretztay]

Hi please help with the following questions:

1. The LCM of 6, 12 and n is 660. Find all the possible values of n.
2. At 5.45pm, Lixin, Khairul and Devi are at the starting point of a 1-km circular path. Lixin takes 18 minutes to walk one round, Khairul needs 360 seconds to run 1 round and Devi cycles 2 rounds in 4 minutes. Find the time when all three of them will next meet.
3. Nora and Amirah work in different companies. Nora has a day off every 4 days while Amirah has a day off every 6 days. Nora's last day off was on 29 April while Amirah's was on 1 May.
(i) When will they next have the same day off?
(ii) Subsequently, how often will they have the same day off?

Thank you in advance!

I would solve the above questions as follows :

1. 660 = 2 x 2 x 3 x 5 x 11
5 x 11 = 55
2 x 5 x 11 = 110
3 x 5 x 11 = 165
2 x 2 x 5 x 11 = 220
2 x 3 x 5 x 11 = 330
Ans : 55, 110, 165, 220 and 330

2. LCM of 18, 6 and 2 is 18.
5.45pm + 18min -> 6.03pm
Ans : 6.03pm

3.(i) 29 Apr – N off
30 Apr
1 May – A off
2 May
3 May – N off
4 May
5 May
6 May
7 May – Both off
Ans : 7 May

(ii) LCM of 4 and 6 is 2 x 2 x 3 = 12
Ans : They will have the same day off on every subsequent 12 days after 7 May.

[MathWithModels]

Anna baked some chicken and beef pies for her friends.45% of the chicken pies and 10% of the beef pies were eaten. Altogether 1/3 of the pies were eaten. In the end, she was left with 10 more chicken pies than beef pies. How many chicken pies did she bake? (Ans 100)

A very nice answer from alfretztay. I'm just adding some detail.

There is more than one way to do this question. We could do it with unit and parts; as a matter of fact, the question has clues which tell us to do just this. Like, more than one ratio is given, but they are ratios which add up to different numbers, not the same number.

So let's bite the bullet, and use units for the chicken pies and parts for the beef pies.

Chicken pies eaten : Chicken pies not eaten
45 : 55, which is the same as
9u : 11u

Beef pies eaten : Beef pies not eaten
10 : 90, which is the same as
1p : 9p

We're told that 1/3 of the pies were eaten; so 2/3 of the pies weren't. This gives us a bar model. I've colour-coded the units and parts to show what comes from where.

If you like bar models,
[Pies eaten][Pies eaten]
[.....Pies not eaten.....]

Pies eaten: 9u (chicken) + 1p (beef)
Pies not eaten: 11u (chicken) + 9p (beef)

And we know the ratio is 1 : 2 (a third of the pies were eaten).
[Pies eaten][Pies eaten] = [Pies not eaten]
9u + 1p + 9u + 1p = 11u + 9p

Adding up the units and parts on the left hand side:
18u + 2p = 11u + 9p

Units on the left, and parts on the right:
18u - 11u = 9p - 2p
7u = 7p

Which means 1 unit = 1 part, and it's all downhill from here. We're told that there were 10 more chicken pies left over than beef pies.
11u (chicken) - 9p = 10

And since 1 unit is exactly the same as 1 part, 9p is the same as 9u, so
11u - 9u = 10 =>2u = 10,
giving u = 5

Total number of chicken pies: 9u (eaten) + 11u (not eaten) = 20u.
As u is 5, Anna made 20 * 5 = 100 chicken pies.

[Blanja85]

Need help:
Jessie went shopping with a sum of money.She spend all of her money in 2 stores.In each store she spend $18 more than half of what she had when she entered the store.
(1) How much did she spend at the second store?
(2) How much money she had first.
Thanks in advance

[justMommy]

Need help:
Jessie went shopping with a sum of money.She spend all of her money in 2 stores.In each store she spend $18 more than half of what she had when she entered the store.
(1) How much did she spend at the second store?
(2) How much money she had first.
Thanks in advance

18 x 2 = $36 (Money spent at second store)
18 x 6 = $108 (Total amount spent = money had at first)

[Blanja85]

Thanks JustMommy.
Can you pls explain it in steps.I dont understand it.