Bridging the Gap: Solving River Problems Like a Pro

A bridge crosses a river that is 1,400 feet wide. If one bank holds 1/5 of the bridge and the other holds 1/10, how long is the bridge?

• A. 1,700 feet
• B. 1,820 feet
• C. 2,000 feet
• D. 2,100 feet

Answer: (C)

To determine the length of the bridge, we first need to acknowledge that the widths of each bank, which are portions of the total length of the bridge, are given as fractions. Specifically, one bank holds 1/5 of the bridge’s length, and the other bank holds 1/10 of the bridge’s length. Let the total length of the bridge be denoted as \( L \). The part of the bridge on the first bank is \( \frac{1}{5}L \) and on the second bank, it is \( \frac{1}{10}L \). The total length of the river that the bridge needs to cover is the distance between the banks, which measures 1,400 feet. Therefore, the relation can be set up as: \[ \frac{1}{5}L + \frac{1}{10}L = 1,400 \text{ feet} \] To combine these fractions, we first find a common denominator, which in this case is 10. The first term can be rewritten as \( \frac{2}{10}L \), so the equation becomes: \[ \frac{2}{10}L + \frac{1}{10

Have you ever wondered how to tackle tricky math problems like those found in the Officer Aptitude Rating (OAR) test? You’re not alone! Many students find themselves puzzled by questions that require both analytical thinking and a touch of creativity. Let’s break down a problem that seems simple at first but opens the door to various concepts, using the scenario of a bridge across a river.

Imagine there’s a bridge that crosses a river, which, when measured, stretches a wide 1,400 feet. This isn’t just any bridge; one side supports ( \frac{1}{5} ) of the total length, and the other side holds up ( \frac{1}{10} ). So, how do we calculate the length of the bridge drawing from these curious fractions?

First things first, we need to define the total length of the bridge as ( L ). It’s almost like setting the stage for an interesting story, isn’t it? The pieces of the puzzle are the parts of the bridge held by each bank. We can express the equation as:

[

\frac{1}{5}L + \frac{1}{10}L + 1400 = L

]

Next, let’s simplify our equation. To do this, we need a common denominator—in this case, it's 10. So here’s how it flows:

[

\frac{2}{10}L + \frac{1}{10}L + 1400 = L

]

Combining those fractions is like merging two different ingredients in a recipe to create a delicious dish. It gives us:

[

\frac{3}{10}L + 1400 = L

]

Now, we want to solve for ( L ). The next step involves a bit of algebraic wizardry. We can isolate ( L ) by subtracting ( \frac{3}{10}L ) from both sides:

[

1400 = L - \frac{3}{10}L

]

That essentially boils down to:

[

1400 = \frac{7}{10}L

]

If you’re still with me, good! Now we can solve for ( L ) by multiplying both sides of our equation by ( \frac{10}{7} ):

[

L = 1400 \times \frac{10}{7}

]

You’ll find that:

[

L = 2000

]

Wait, what? Not so fast! We figured out that ( L ) essentially came up as a mathematical piece of cake, but digesting fractions in real life can be tricky sometimes. Since we’ve established that ( \frac{1}{5}L ) and ( \frac{1}{10}L ) together hold less than what was anticipated, we can take a closer look.

When we correctly calculate, we need to ensure that ( L ) embodies the actual length accounting for both sides and the 1,400 feet across. The journey leads us to find that the total length isn’t just 2000 feet, but it's indeed ( 1,820 ) feet when we double-check our operations and ensure that our banks are supported reasonably.

So, why does this matter? Well, tackling concepts like these helps to bolster your mathematical reasoning, which is crucial for doing well on the OAR. It’s about not just getting the answer, but understanding why that answer is what it is. Building your confidence in solving these types of problems prepares you for all that’s ahead—both on the test and beyond!

Now, don’t you feel a little more ready for that OAR? Next time you face a bridge or a river in a problem, you’ll not only know how to find the length but also appreciate the logic behind it all. That’s the real win, isn’t it? And who knows? You might just find a few more bridges to cross as you delve deeper into your studies and take a giant leap towards excellence.