Question

y is directly proportional to the square root of ( x-3 ). When x = 28, y = 20. Find y when x = 39.

Answer 1

Answer:

• 24

Step-by-step explanation:

y is directly proportional to the square root of ( x-3):

• y = k$\sqrt{x-3}$, where k is the coefficient of proportionality

Given:

• y is 20 when x is 28

Find k:

• 20 = k$\sqrt{28-3}$
• 20 = k* 5
• k = 20/5
• k = 4

Find y when x = 39:

• y = 4$\sqrt{39-3}$
• y =4$\sqrt{36}$
• y = 4*6
• y = 24

Answer 2

Answer:

y = 24

Step-by-step explanation:

Given y is directly proportional to $\sqrt{x-3}$ then the equation relating them is

y = k$\sqrt{x-3}$ ← k is the constant of proportion

To find k use the condition when x = 28, y = 20 , then

20 = k × $\sqrt{28-3}$ = k × $\sqrt{25}$ = 5k ( divide both sides by 5 )

4 = k

y = 4 $\sqrt{x-3}$ ← equation of proportion

When x = 39 , then

y = 4 × $\sqrt{39-3}$ = 4 × $\sqrt{36}$ = 4 × 6 = 24