Solve for the unknown: 89% of a number plus 365 equals 1075.22. What is the number?

Difficulty: Easy

Correct Answer: 798

Explanation:


Introduction / Context:
This linear percentage equation involves isolating the unknown number from a mixed expression containing a percent of the number plus a constant. Converting to decimal and solving step-by-step yields the exact result.

Given Data / Assumptions:

  • Equation: 0.89x + 365 = 1075.22.
  • x represents the unknown number.


Concept / Approach:
Subtract the constant to isolate the percentage term, then divide by the decimal percentage (0.89) to obtain x. This is a direct algebraic manipulation.

Step-by-Step Solution:

0.89x + 365 = 1075.22.0.89x = 1075.22 − 365 = 710.22.x = 710.22 / 0.89.Compute: 0.89 * 800 = 712; reduce by 0.89 * 2 = 1.78 to reach 710.22 → x = 800 − 2 = 798.


Verification / Alternative check:
Plug back: 0.89 * 798 = 710.22; add 365 gives 1075.22, matching exactly.


Why Other Options Are Wrong:

  • 897, 898, 752: Substitution fails to reach 1075.22 when processed through 0.89x + 365.


Common Pitfalls:
Dividing by 89 instead of 0.89, or rounding too early and losing accuracy. Keep at least two decimals until the final check.


Final Answer:

798

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