## Question

secondary 4 | A Maths

Anyone can contribute an answer, even non-tutors.

##### Kathy2

chevron_right chevron_right

Thank you

Date Posted: 4 months ago
Views: 38
Eric Nicholas K
4 months ago
You can post the next one, I am free to write now even while I am in the middle of tuition

clear {{ downvoteCount * -1 }} Downvotes
1st
I hope this solution helps you!
Date Posted: 4 months ago
Kathy2
4 months ago
I can’t even see it
Eric Nicholas K
4 months ago
Will do my posting later on a question by question basis in the middle of my tuition
clear {{ downvoteCount * -1 }} Downvotes
Date Posted: 4 months ago
clear {{ downvoteCount * -1 }} Downvotes
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.
Date Posted: 4 months ago
Eric Nicholas K
4 months ago
clear {{ downvoteCount * -1 }} Downvotes
Two almost symmetrical approaches to solve Q9
Date Posted: 4 months ago
clear {{ downvoteCount * -1 }} Downvotes
Q10
Date Posted: 4 months ago
clear {{ downvoteCount * -1 }} Downvotes
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.
Date Posted: 4 months ago
clear {{ downvoteCount * -1 }} Downvotes