Kuasimi:

Oh..why not 510ml as total liquid is 510ml

That's because it is a controlled set up, therefore, know the motive of the question, what Andy wants to find out in the experiment.
[quote]Andy wanted to find out if bleach affects the growth of duckweeds. He set up an experiment with the information below .[/quote]So, you know that Andy wanted to find out if bleach affects the growth of duckweeds.

So the independent variable would be the amount of bleach used.

Therefore the controlled variable would be the number of duckweeds and the amount of water used.

So Kuasimi, you cannot calculate the total amount of water and bleach together. As the question says that Andy wanted to see if the amount of bleach would affect the growth of duckweeds, so you cannot change the number of duckweeds and the amount of water used, or else the experiment would be an unfair experiment. Hope you might help you understand your misconception. I hope I can at least help you to understand. Correct me if I am wrong. Thnks.

angel:

Hi, may I check,


How to do questions like this?
Which fraction is larger than 1/3?
1) 7/21
2) 6/17
3) 4/13
4 3/11

Method: Use decimal to compare. (*I used calculator to calculate the decimal)
1/3 =0.3333333333
______________________________________________________________
1. 7/21=0.3333333333
2. 6/17=0.3529411765
3. 4/13=0.3076923077
4. 3/11=0.2727272727

______________________________________________________________
Method: If I did not use calculator to calculate, you can calculate the decimal to 3 decimal points would do

1. 7/21=0.333
2. 6/17=0.352
3. 4/13=0.307
4. 3/11=0.272
______________________________________________________________
Therefore Choice Number 2 is the answer as 6/17(0.3529411765) is bigger than 1/3(0.3333333333)

alfretztay:

questionable_i:

Can any one help me with this question?

_____________________________________________________________
1 bag and 2 pencil boxes cost $d.
2 bags, 4 pencil boxes and 4 erasers cost $28.

(a) How much does one eraser cost? Express your answer in terms of d.
(b) If d=13, find the cost of an eraser.

I would solve the above as follows :

(a)
1 bag + 2 pencil boxes ——- $d
2 bags + 4 pencil boxes + 4 erasers ——– $28
1 bag + 2 pencil boxes + 2 erasers ——- $28/2 = $14
2 erasers ——- $(14 – d)
1 eraser ——- $(14 – d)/2 = $(7 - d/2)

(b)
1 eraser ——- $(14 – 13)/2 = $0.50

Ans : $(7 – d/2); (b) $0.50.

:thankyou:

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Can any one help me with this question?

_____________________________________________________________
1 bag and 2 pencil boxes cost $d.
2 bags, 4 pencil boxes and 4 erasers cost $28.

(a) How much does one eraser cost? Express your answer in terms of d.
(b) If d=13, find the cost of an eraser.

nicnac:

questionable_i:

I need some help for this question:

Caleb and Dan had some coins. Caleb had only 50 cent coins and Dan had only 20 cent coins. At first, the number of coins Caleb had was 1/3 the number of coins that Dan had. After Dan gave Caleb $8, Dan had 2/3 of his original number of coins left. What was the difference in the amount of money that Caleb and Dan had in the end?

Answer :$12 ?

Dan
$8 --> 40 20-cents coins
1/3 --> 40
3/3 --> 120
In the end, Dan has 80 20cents coins --> $16

Caleb,
$8--> 16 50-cent coins
At first Caleb has (1/3 of number of coins of Dan) 1/3* 120= 40
In the end, Caleb has 56 50-cents coins --> $28

Difference= 28 - 16=$12

Yup, the answer is $12. :thankyou:

Do more revision.

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I need some help for this question:

Caleb and Dan had some coins. Caleb had only 50 cent coins and Dan had only 20 cent coins. At first, the number of coins Caleb had was 1/3 the number of coins that Dan had. After Dan gave Caleb $8, Dan had 2/3 of his original number of coins left. What was the difference in the amount of money that Caleb and Dan had in the end?

guest2013:

questionable_i:

Can anyone help me?


Loha bought 3 1/2kg of flour to bake a lemon cake and some cookies for a party. She used 1/4 of the flour to bake the lemon cake and 3/5 of the remaining flour to bake the cookies. How much flour did she have left?

Suggested answer:

1/4 of flour to bake cake, therefore left 3/4 of flour.
3/5 of remaining (3/4 of the flour) bake cookies, left 2/5 of the 3/4 flour, 2/5 x 3/4 = 3/10 of flour left.

Amount of flour left will be
3 1/2kg x 3/10 = 1.05 kg or 1 1/20kg.

:thankyou: