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The radius of a circular disc is increasing at a constant rate of 0.003cm/s. Find the rate at which the area is increasing when the radius is 20cm.

The rate at which the area is increasing, dA/dt, can be written with terms we know or can find out easily: dA/dt=dA/dr x dr/dt.Area of a disc, A = (pi)r^2dA/dr=2(pi)rRate of change of radius, dr/dt=0.003cm/s...
HH
Answered by Henry H. • Maths tutor
12489 Views

Factorise 15r+10

Step 1) look at the numbers Both 15 and 10 are factors of 5 step 2 ) look at the letters there is only one letter 'r' after the 15 step 3) there is only one possible thing that can be factorised out therefor...
JL
Answered by Judy L. • Maths tutor
10567 Views

How do I solve a simple simultaneous equation?

Simultaneous equations pop up all the time in maths, science, and engineering, so being able to solve them is really useful. Although they can look a bit daunting at first, the same general rules apply to so...
JM
Answered by Joe M. • Maths tutor
5306 Views

Trolley A weighs 5kg and is moving at 15m/s to the right. It collides with a stationary Trolley B, weighing 10kg more than Trolley A. After the collision they move off together. Calulate the velocity that they move off with.

To start with, we should work out all of the quantities we need: Mass of Trolley A: M A = 5kg Mass of Trolley B: B weighs 10kg more than A --> Therefore M B = 10 + 5 = 15kg Mass of Both Trolleys together:...
JD
Answered by Joshua D. • Physics tutor
8125 Views

Solve the equation log(1-x) - log(x) = 1 where log() is the logarithmic function, base 10.

From the rules of logarithms, we know that: log(A) - log(B) = log(A/B) and thus: log(1-x) - log(x) = log[(1-x)/x] Therefore from the question, we know: log[(1-x)/x] = 1 If we then take both sides of the equa...
JD
Answered by Joshua D. • Maths tutor
22786 Views