Difficulty: Medium
Correct Answer: 34
Explanation:
Introduction:
This is a standard linear equation word problem involving two parts of a given total. The problem asks you to split 54 into two numbers so that a weighted sum (10 times one part plus 22 times the other) equals 780. Such questions test your ability to convert a word statement into a pair of algebraic equations and solve them consistently.
Given Data / Assumptions:
Concept / Approach:
Use simultaneous equations. From the total equation, express one variable in terms of the other (for example, y = 54 - x). Substitute this into the second equation to obtain a single equation in x. Solve for x, compute y, and determine which is larger. This is a direct application of solving two linear equations in two unknowns.
Step-by-Step Solution:
Let first part = x and second part = y.Total: x + y = 54 => y = 54 - x.Condition: 10x + 22y = 780.Substitute y: 10x + 22(54 - x) = 780.10x + 1188 - 22x = 780.-12x + 1188 = 780.-12x = 780 - 1188 = -408.x = (-408)/(-12) = 34.Then y = 54 - 34 = 20.So the bigger part is 34.
Verification / Alternative check:
Check the condition: 10 * 34 + 22 * 20 = 340 + 440 = 780, which matches exactly. The total 34 + 20 = 54 is also satisfied. Thus the split (34, 20) is correct and 34 is indeed the larger part.
Why Other Options Are Wrong:
24, 44, 30, 20: none of these values, when paired with 54 minus that value, satisfy the equation 10x + 22y = 780. A quick substitution shows the weighted sum is different from 780.
Common Pitfalls:
Confusing which coefficient (10 or 22) multiplies which part when writing the equation.Arithmetic errors while simplifying 10x + 22(54 - x).Forgetting to verify both the total 54 and the weighted sum 780 after solving.
Final Answer:
34
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