Any idea how to demonstrate the link between MD and units?


Question: There were some rules and erasers in the box. When Rizal took out 20 rulers, 1/3 of the remaining items in the box were rulers. If he had taken out 75% of the erasers, then 2/9 of the remaining items in the box would have been erasers. How many rulers were there in the box?

Ngee Ann P6 Math SA1 2012


Help please with this question - trying to show child MD and UP methods.

There were some pens and pencils in the box. If Arif took out 140 pencils, 1/3 of the remaining items in the box were pencils. If he took out 25% of the pens, then 1/4 of the remaining items in the box were pens.
(a) how many pens were there in the box?
(b) how many pencils were there?

Can anybody recommend a good book about ratios?


Having trouble with this problem because 2 variables change.

INN Store imported Notie mobile phones and Dricsin mobile phones in the ratio 8:5. After selling 120 Notie mobile phones and 135 Dricsin mobile phones, the ratio of Notie mobile phones and Dricsin mobile phones left was 8:3. How many Notie mobile phones did the store import?

Help needed (Nanyang P6 CA1 2011). Thank you.


The mass of four sacks of rice A, B, C, D were recorded. 3 sacks of rice were weighed at a time.
Sacks A,B and C weighed a total of 55 kg
Sacks B,C and D weighed a total of 56 kg
Sacks A,C and D weighed a total of 57 kg
Sacks A,B and D weighed a total of 58.5 kg

What was the total mass of Sack B and Sack D?

Help needed (Nanyang P6 CA1 2011)


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

Nanyang P6 2011 CA1

Q16) Sushila went shopping. She spent $588 on 2 dresses, 3 skirts 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 on the sunglasses was 1/3 of the total amount spent on dresses and skirts.
(a) how much did she spend on the 2 pairs of sunglasses?
(b) what was the cost of the third skirt if the average cost of the other 2 skirts was $88?

Looking for a model to help explain to my kid.

Is there a simpler method to solve this question (extract from My Pals are Here, Maths Homework, Primary 6A)


Question
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Keith and Shawn each have some money. If Keith spends $38, the ratio of the amount of money Keith has to the amount of money Shawn has will become 2:5. If Shawn spends $38, the ratio will become 8:13. How much money does each boy have?

Answer
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Eqn 1: (K-38)/S = 2/5 -> 2S = 5K-190
Eqn 2: K/(S-38) = 8/13 -> 13K = 8S-304

Substitute eqn 1 into eqn 2 to get
13K = 4 (5K-190) - 304
K = 152

Solve eqn 1 using K=152

S = ((5x152) -190)/2 = 285

Keith has $152 and Shawn has $285

Would somebody please check this (extract from My Pals are Here, Maths Homework - P6)


Question
-----------
The ratio of Jame’s age to Andy’s age is 2:7. In 8 years time, the ratio will become 2:5. Find Jame’s present age.

Answer
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Eqn 1: J/A = 2/7 -> 7J=2A

Eqn 2: (J+8) / (A+8) = 2/5 -> 5J + 40 = 2A + 16

Substitute eqn 1 into eqn 2

5J + 40 = 7J +16
7J-5J = 40-16
2J = 24
J = 12
James present age is 12 years old.

James : Andy
2 : 7
12 : 42

Andy is 42 years old.

After 8 years
James : Andy
2 : 5
20 : 50 (or 12+8 : 42+8)

thank you both for the answer and model. Cheers.

Can anybody provide the model for this problem?


John has 3 times as many stamps as Peter. When John loses 420 stamps and Peter loses 40 stamps, Peter has twice as many stamps as John. How many stamps does each of them have at first?