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secondary 4 | A Maths
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kathy2
Kathy2

secondary 4 chevron_right A Maths chevron_right Singapore

Thank you

Date Posted: 1 month ago
Views: 28
Eric Nicholas K
Eric Nicholas K
1 month ago
You can post the next one, I am free to write now even while I am in the middle of tuition

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Gavin
Gavin's answer
2 answers (A Helpful Person)
1st
I hope this solution helps you!
kathy2
Kathy2
1 month ago
I can’t even see it
Eric Nicholas K
Eric Nicholas K
1 month ago
Will do my posting later on a question by question basis in the middle of my tuition
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Jiayang
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1883 answers (Tutor Details)
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Eric Nicholas K
Eric Nicholas K's answer
2941 answers (Tutor Details)
Q8

Kathy, this topic is basically understanding how things change with time, since rate is related to the time t. We use chain rule formulas involving t, such as dV/dt = dV/dh dh/dt to solve such questions.

The steps to solve this question are as follows.

1. Extract out useful information and transform them into words. Here, the depth increases at 2 cm/s, so we transform it to dh/dt = 2 cm/s.

2. We find out what our wanted quantity is. Here, it’s dV/dt.

3. We express dV/dt in terms of dV, dh and dt. Here, it’s dV/dt = dV/dh dh/dt (think of this as “cross multiplication”), so we need to find out what dV/dh is. It’s the rate of change of V with respect to h, so we need to know what V is in terms of h. It’s given in this question. At other times, you need to form your own equation (such as area of a circle A = #r2).

4. Finally, multiply them out to get the value.
Eric Nicholas K
Eric Nicholas K
1 month ago
Kathy, my phone is ok already so I can continue to help you do some questions.
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Eric Nicholas K
Eric Nicholas K's answer
2941 answers (Tutor Details)
Two almost symmetrical approaches to solve Q9
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Eric Nicholas K
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2941 answers (Tutor Details)
Q10
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Eric Nicholas K
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2941 answers (Tutor Details)
Q11

The fact that V = 8x2 and not some x3 shows that the volume of the cuboid only depends on the dimensions of the base, while the height is fixed at 8 cm.
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Eric Nicholas K
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2941 answers (Tutor Details)
Q12