Question

The cost of a circular table is directly proportional to the square of its radius. A table with a radius of 40cm cost £90.
What is the cost of a table with a radius of 60cm?

Answer 1

Resposta: £202,5

Explicação passo a passo:

If the cost is directly proporcional by the square radius, then a table with 60 cm radius costs more than a table with 40 radius.

Doing the proportion, we have:

$40^{2} = 90$

$60^{2} = X$

Then:

1600 = 90
3600 = X

cross multiplying:

1600 . X = 3600 . 90

1600x = 324000

$X = \frac{324000}{1600}$

X = 202,5

The cost of a table with radius of 60cm is £202,5