Suz855:

pinkapple:

[quote=\"Suz855\"]Pls help


Estimate cube root of 521 divide by 2.01 correct to 1 significant figure

Thks

521 ~ 512 (nearest cube number)
Cube root of 512 = 8

2.01 ~ 2
8 / 2 = 4

Thks pinkapple, the teacher's answer estimate the cube root to the next higher value which is 729 n answer given was 5, do you think the teacher's answer was wrong?[/quote]Dear Suz855

I will say your teacher'a answer is wrong. If you compute, the exact answer is 4.003. Hence, the closest estimate is 4, and NOT 5.

redruby:

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Answer is diagram (3)

Reason: the experiment is to find out the effect of light on the plants in the beaker of water. In order to observe and measure the effect, the experiment has to be set up so that one set is with light shining on the beaker with the plants, and another set as \"control\" without the light. The difference in the growth pattern of the plants between the two set up can then be compared, and conclusion can be drawn on the effect of light on the plants.

By the way, why diagram (4), although it is without the light also, is wrong is because there is only 1 plant in the beaker. When experiment is set up to compare with a \"control\" set, everything must be kept identical except the 'factor' which you want to test on - ie. the light source in this question.

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Anne


Sorry I have to put in my comment with regard to your earlier remark to clarify on your understanding of elkniwt’s solution. The solution was not working ‘from the back’, or backwards. It is to recognize the expression, and put it, into the generic form of a^2 + 2ab + b^2, then factorize into (a + b)^2. That is

(a - 2b)^2 + 2c(a - 2b) + c^2
Factorize,
= (a - 2b + c)^2

Hope this helps.

Glad to be of help. If you encounter any difficult questions which you can’t solve in the future, feel free to post them out. There are many in this forum who are willing to help you.

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Dear Wimpy Kid


I believe the last few posted questions are at Sec4 level.

Once you practise more and more on every topic, you will be able to apply all the properties, formulas, and theorems speedily and with ease. Have fun.

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