If y is directly proportional to x, and when x = 2, y = 20, what is the value of y when x = 9?

The core concept here is direct proportionality. If y is directly proportional to x, their relationship can be expressed as y = kx, where 'k' is the constant of proportionality.

• Correct Option D (90): First, find 'k' using the given values: when x = 2, y = 20. So, 20 = k * 2, which means k = 10. The relationship is y = 10x. Now, substitute x = 9 into this equation: y = 10 * 9 = 90.
• Distractor A (20): This is the value of y when x was 2, not when x is 9.
• Distractor B (35): This is an incorrect calculation, not following the direct proportionality rule.
• Distractor C (45): This might result from an incorrect constant of proportionality or calculation error.