Collin's Cambridge IGCSE Maths
Student's book by Chris Pearce

Maths Question:
page 517
Exercise 27M, Question 5

Lead has a density of 11.35 g/cm3. Calculate the maximum number of lead spheres of radius 1.5 mm that can be made from 1 kg of lead.

Volume of Sphere

6231 spheres can be made from 1 kg of lead

Step-by-step explanation:

Given Density of lead d = 11.35 gm/cm³

Let the maximum number of spheres that can be made with 1 kg of lead = n

Radius of sphere r = 1.5 mm = 0.15 cm

Volume of Sphere =

Volume of one sphere V = (4/3) * 22.7 * r³

Volume of n spheres = n * (4/3) * 22.7 *r³    ….. Eq (1)

Total mass of lead m = 1kg = 1000gm ...Eq (2)

Equating the above two equations

n × V × d = m

n × (4/3) × 22.7 × ( 0.15 )³ = 1000

Therefore calculating n= 6231.45

But considering the whole number, 6231 spheres can be made from 1 kg of lead.

the answer is 15% decrease

the total estimated nappy use.=10,500,000

step-by-step explanation:

given that on an average the average baby uses 3528 napkins.

in a particular year 2014, the number of births were 299697 in new south wales.

rounding off the number of births to the nearest hundred thousand we have

no of birtsh = 300000

also rounding off the average usage to nearst thousand we get

average use of a baby = 3500

hence total number of nappy estimated to be used = 3500x300000

= 10,500,000

answer is 10,500,000 nappies