Question

stion 1-1
if y varies directly with x and y = 28 when x = 4, what is y when x = 3?
□ y = 21
□ y = \frac{7}{3}
□ y = \frac{1}{21}
□ y = \frac{3}{7}

Explanation:

Step1: Define direct variation

For direct variation, \( y = kx \), where \( k \) is the constant of variation.

Step2: Find \( k \)

Given \( y = 28 \) when \( x = 4 \), substitute into \( y = kx \):
\( 28 = k \times 4 \)
Solve for \( k \): \( k=\frac{28}{4}=7 \).

Step3: Find \( y \) when \( x = 3 \)

Now, use \( k = 7 \) and \( x = 3 \) in \( y = kx \):
\( y = 7 \times 3 = 21 \).

Answer:

\( y = 21 \) (corresponding to the option \( y = 21 \))