The number of uniform spherical shots that can be made from a given mass of lead varies inversely to the cube of the radius. When the radius is 1mm the number of shots made is 2744. How many shots of radius 1.4mm can be made from the same mass.

The key to long questions like these is picking out the key information quickly.
We have 2 pieces of information we are interested in, the number of shots and the radius of each shot, so let's assign them a letter.
let n = # of shots that can be made
let r = radius of each shot
We know, from the question, the number of shots is inverseley proportional to the radius of each shot. i.e. 
n = k/r3
We see in the equation above that n is equal to some number ( a constant ) divided by r3. If we could find this constant we would be able to substitute in our radius to find the number of shots.
To find the constant let's substitute in the information we already have
2744 = k/13
therefor k = 2744
Now it should be easy to get that n to pop out
n = 2744/1.43
Although you will most likely use a calculator for this last step, write down the calculation anyway so the examiner knows what you have done. 
n = 1000

JJ
Answered by Joshua J. Maths tutor

4249 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Jodie buys 12 cans of cola. There are 330 ml of cola in each can. Rob buys 4 bottles of cola. There is 1 litre of cola in each bottle. Rob buys more cola than Jodie. How much more?


An ordinary, fair sided dice is rolled 480 times. How many times is the number 3 expected?


There are 40 counters in a bag. 13 are red, 20% are green and the rest are yellow. What proportion of counters are yellow?


How do I use trigonometric ratios to work out lengths in right-angled triangles?


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences