If area of a circle varies directly as the cube of the radius, when the area is 625cm the radius is 5cm. calculate the area of a circle of radius 8

2560 cm²

Step-by-step explanation:

Given that the area (A) varies directly as the cube of the radius (r) then the equation relating them is

A = kr³ ← k is the constant of variation

To find k use the condition A = 625 when r = 5

k = = = = 5

A = 5r³ ← equation of variation

When r = 8, then

A = 5 × 8³ = 5 × 512 = 2560 cm²

rick has $1400 and sally has $1500

step-by-step explanation:

to find amount of money rick has after 10 years :

principal = $1000 , time = 10 years , rate = 4% annually

to find amount of money sally has after 10 years :

her friend gives to pay her $50 per year, therefore money she has after 10 years = 50 × 10 = $500

also, sally gets $1000 after 10 years,

therefore, total amount of money sally has after 10 years = 500 + 1000 = $1500

so, after 10 years : rick has $1400 and sally has $1500

i got 10.28 but that rounds up to 10.3