Question 21

X equals 540.

To solve the proportion 9 : X :: 5 : 300, we can set up the equation 9/5 = X/300. Cross-multiplying leads to 9 * 300 = 5 * X, which simplifies to X = (9 * 300) / 5. This calculation results in X being equal to 540.

A) 450

Option A is incorrect because if X were 450, the cross-multiplication would yield 9 * 300 = 5 * 450, which simplifies to 2700 = 2250, a false statement. Thus, this value does not satisfy the proportion.

B) 540

Option B is correct. Substituting 540 into the proportion gives us 9/5 = 540/300. Cross-multiplying confirms the equality as 9 * 300 = 5 * 540, which simplifies to 2700 = 2700, validating that this option maintains the proportional relationship.

C) 600

Option C is incorrect because if X were 600, then 9/5 would not equal 600/300. Cross-multiplying would yield 9 * 300 = 5 * 600, or 2700 = 3000, which is not true. Therefore, this choice fails to satisfy the proportion.

D) 480

Option D is also incorrect. Substituting 480 into the proportion results in 9/5 = 480/300. Cross-multiplying gives 9 * 300 = 5 * 480, simplifying to 2700 = 2400, which is false. Hence, this value does not maintain the ratio.

Conclusion

The correct answer is 540 because it accurately satisfies the proportion established in the question. All other options fail to maintain the equality required by the ratio, demonstrating that only 540 is the valid solution for X in this context.