F is inversely proportional to d 2 . When F = 8 , d = 6 Work out d (positive value rounded to 2 DP) when F = 7

d ≈ 6.41

Step-by-step explanation:

Given that F is inversely proportional to d² then the equation relating them is

F = ← k is the constant of proportion

To find k use the condition when F = 8, d = 6 , then

8 = = ( multiply both sides by 36 )

288 = k

F = ← equation of proportion

When F = 7 , then

7 = ( multiply both sides by d² )

d² × 7 = 288 ( divide both sides by 7 )

d² = ( take the square root of both sides )

d = ± ≈ ± 6.41

The positive value of d is 6.41 ( to 2 dec. places )

when F = 7, d = 6.41

Step-by-step explanation:

We know that when 'y' varies inversely with 'x', we get the equation

y ∝ 1/x

y = k/x

where 'k' is called the constant of proportionality

Given that F is inversely proportional to d.

F ∝ 1/d

F = k /d²

When F = 8, d = 6, we need to find k

k = Fd²

k = 8×(6)²=288

Now, we need to find d when F = 7

so substitute k = 288, F = 7 in the equation

F = k /d²

d² = k/F

d² = 288/7

but, we need to take the positive value of d, so

Therefore,

when F = 7, d = 6.41

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