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Linda put an amount of money into each of two new investments, A and B, that pay simple annual interest. If the annual interest rate of investment B is \(1\frac{1}{2}\) times that of investment A, what amount did Linda put into investment A
Let's restate what we're looking for: What specific dollar amount did Linda invest in investment A?
To find a specific dollar amount, we need either:
Key insight: When a problem gives us relationships between variables but not actual values, it often signals insufficient information.
Let's think about what this reveals. Investment B earned exactly 3× as much interest as A (\(\$150\) vs \(\$50\)). But wait—B's interest rate is only 1.5× A's rate. How can B earn 3× the interest with only 1.5× the rate?
The answer: B must have 2× as much principal invested!
But here's the crucial question: What's the actual interest rate? Let's test two scenarios:
Scenario 1: If A's rate = 5%
Scenario 2: If A's rate = 10%
Different rates give us different principal amounts. We cannot determine the exact amount Linda invested.
Statement 1 alone is NOT sufficient.
This eliminates answer choices A and D.
Now let's forget Statement 1 completely and analyze Statement 2 independently.
The amount Linda invested in B is twice the amount she invested in A.
This gives us a ratio: \(\mathrm{B} = 2\mathrm{A}\). But without knowing:
We have infinite possibilities. For example, Linda could have invested:
Statement 2 alone is NOT sufficient.
This eliminates answer choice B.
Here's where it gets interesting: Statement 2 just confirms what we already figured out from Statement 1! It doesn't add any new information.
We still have the fundamental constraint from Statement 1:
Principal in A × Rate of A = \(\$50\)
Since we don't know the actual interest rate, this equation has infinite solutions:
Even combining both statements, we cannot determine the exact amount Linda invested in A. The statements together are NOT sufficient.
This eliminates answer choice C.
The statements together are not sufficient because we still don't know the actual interest rate, leaving us with infinite possible values for the principal amount in investment A.
Answer Choice E: "The statements together are not sufficient."